Customary International Humanitarian Law

INTERNATIONAL COMMITTEE OF THE RED CROSS

CUSTOMARY
INTERNATIONAL
HUMANITARIAN LAW

VOLUME I

RULES

Jean-Marie Henckaerts and Louise Doswald-Beck
With contributions by Carolin Alvermann,
Knut Dörmann and Baptiste Rolle

PUBLISHED BY THE PRESS SYNDICATE OF THE UNIVERSITY OF CAMBRIDGE
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© International Committee of the Red Cross 2005

This book is in copyright. Subject to statutory exception
and to the provisions of relevant collective licensing agreements,
no reproduction of any part may take place without
the written permission of Cambridge University Press.

First published 2005
Reprinted 2005
Reprinted with corrections 2006

Printed in the United Kingdom at the University Press, Cambridge

Typeface Trump Medieval 10/13 pt. System LATEX 2e [TB]

A catalogue record for this book is available from the British Library

ISBN 0 521 80899 5 hardback
ISBN 0 521 00528 0 paperback

Hardback also available as:
ISBN 0 521 53925 0 set including Volume II

CONTENTS

FOREWORD BY DR. JAKOB KELLENBERGER
President of the International Committee of the Red Cross

The laws of war were born of confrontation between armed forces on the battle- field. Until the mid-nineteenth century, these rules remained customary in nature, recognised because they had existed since time immemorial and because they corresponded to the demands of civilisation. All civilisations have developed rules aimed at minimising violence – even this institutionalised form of violence that we call war – since limiting violence is the very essence of civilisation.

By making international law a matter to be agreed between sovereigns and by basing it on State practice and consent, Grotius and the other founding fathers of public international law paved the way for that law to assume universal dimensions, applicable both in peacetime and in wartime and able to transcend cultures and civilizations. However, it was the nineteenth-century visionary Henry Dunant who was the true pioneer of contemporary international humanitarian law. In calling for “some international principle, sanctioned by a Convention and inviolate in character” to protect the wounded and all those trying to help them, Dunant took humanitarian law a decisive step forward. By instigating the adoption, in 1864, of the Geneva Convention for the amelioration of the condition of the wounded and sick in armed forces in the field, Dunant and the other founders of the International Committee of the Red Cross laid the cornerstone of treaty-based international humanitarian law.

This treaty was revised in 1906, and again in 1929 and 1949. New conventions protecting hospital ships, prisoners of war and civilians were also adopted. The result is the four Geneva Conventions of 1949, which constitute the foundation of international humanitarian law in force today. Acceptance by the States of these Conventions demonstrated that it was possible to adopt, in peacetime, rules to attenuate the horrors of war and protect those affected by it.

Governments also adopted a series of treaties governing the conduct of hostilities: the Declaration of St Petersburg of 1868, the Hague Conventions of 1899 and 1907, and the Geneva Protocol of 1925, which bans the use of chemical and bacteriological weapons.

These two normative currents merged in 1977 with the adoption of the two Protocols additional to the 1949 Geneva Conventions, which brought up to date both the rules governing the conduct of hostilities and those protecting war victims.

More recently, other important conventions were added to this already long list of treaties, in particular the 1980 Convention on Certain Conventional Weapons and its five Protocols, the 1997 Ottawa Convention on the Prohibition of Anti-Personnel Landmines, the 1998 Statute of the International Criminal Court, the 1999 Protocol to the 1954 Convention for the Protection of Cultural Property in the Event of Armed Conflict and the 2000 Optional Protocol on the Involvement of Children in Armed Conflict.

This remarkable progress in codifying international humanitarian law should not, however, cause us to ignore customary humanitarian law. There are three reasons why this body of law remains extremely important.

First, while the Geneva Conventions enjoy universal adherence today, this is not yet the case for other major treaties, including the Additional Protocols. These treaties apply only between or within States that have ratified them. Rules of customary international humanitarian law on the other hand, sometimes referred to as “general” international law, bind all States and, where relevant, all parties to the conflict, without the need for formal adherence.

Second, international humanitarian law applicable to non-international armed conflict falls short of meeting the protection needs arising from these conflicts. As admitted by the diplomatic conferences that adopted them, Article 3 common to the Geneva Conventions and Protocol II additional to those Conventions represent only the most rudimentary set of rules. State practice goes beyond what those same States have accepted at diplomatic conferences, since most of them agree that the essence of customary rules on the conduct of hostilities applies to all armed conflicts, international and non-international.

Last, customary international law can help in the interpretation of treaty law. It is a well-established principle that a treaty must be interpreted in good faith and with due regard for all relevant rules of international law.

With this in mind, one better understands the mandate assigned to the ICRC by the 26th International Conference of the Red Cross and Red Crescent (Geneva, 1995), when the organization was asked to:

prepare, with the assistance of experts in international humanitarian law representing various geographical regions and different legal systems, and in consultation with experts from governments and international organisations, a report on customary rules of international humanitarian law applicable in international and non-international armed conflicts, and to circulate the report to States and competent international bodies.

The ICRC charged two members of its Legal Division with the task of carrying out this study. Under the guidance of a Steering Committee composed of 12 experts of international repute, the ICRC engaged in a large-scale consultation process involving over 100 eminent authorities. Considering this report primarily as a work of scholarship, the ICRC respected the academic freedom both of the report’s authors and of the experts consulted, the idea being to capture the clearest possible “photograph” of customary international humanitarian law as it stands today.

The ICRC believes that the study does indeed present an accurate assessment of the current state of customary international humanitarian law. It will therefore duly take the outcome of this study into account in its daily work, while being aware that the formation of customary international law is an ongoing process. The study should also serve as a basis for discussion with respect to the implementation, clarification and development of humanitarian law.

Lastly, the ICRC is pleased that this study has served to emphasise the universality of humanitarian law. All traditions and civilizations have contributed to the development of this law, which is today part of the common heritage of mankind.

The ICRC would like to express its deep gratitude to the experts who gave freely of their time and expertise, to the staff of its Legal Division, and in particular to the authors, who, in bringing this unique project to its conclusion, refused to be discouraged by the enormity of the task.

In presenting this study to the States party to the Geneva Conventions, to National Red Cross and Red Crescent Societies and other humanitarian organisations, to judges and scholars and to other interested parties, the ICRC’s sincere hope is that it will clarify the meaning and significance of a number of rules of international humanitarian law and that it will ensure greater protection for war victims.

FOREWORD BY DR. ABDUL G. KOROMA
Judge at the International Court of Justice

Sadly, it cannot be said that the incidence of armed conflict has become any rarer since the end of the Second World War. Rather, a host of conflicts across the world, both international and non-international, have highlighted as never before the extent to which civilians have become targets and the growing need to ensure the protection of the wounded, the sick, detainees and the civilian population afforded to them by the rules of international humanitarian law. Opinions vary as to the reason for the increasing number of violations of international humanitarian law. Is it a lack of awareness of the rules on the part of those who should observe them? Is it the inadequacy of the rules even where they are known? Is it weak mechanisms for enforcing the rules? Or is it sheer disregard for the rules? To some extent, there is truth in each. For international humanitarian law to be more effective, not one but all of these facets of the problem need to be addressed. Clearly, the first step in achieving the goal of universal respect for humanitarian rules must be the articulation of what the rules require; only then can the question of how to improve upon them be considered.

This study of customary international humanitarian law and its role in protecting the victims of war is both timely and important for a number of reasons. The relevant treaty law covers a wide variety of aspects of warfare, but treaty law, by its very nature, is unable to provide a complete picture of the state of the law. While treaties bind those States that have adhered to them, without the existence of customary law, non-parties would be free to act as they wished. In addition, because they are written down, treaty rules are well defined and must be clear as to the standard of conduct they require; but since a treaty is the result of an agreement between the parties, the instruction provided by a treaty rule is only as useful as the degree of genuine agreement achieved. Written rules cannot be vague or open to divergent interpretations. Customary international law, while being notorious for its imprecision, may be no less useful than treaty law, and may in fact actually have certain advantages over it. For example, it is widely accepted that general customary international law binds States that have not persistently and openly dissented in relation to a rule while that rule was in the process of formation. Also, one of the most important bases for the success of a treaty regime is the extent of the political will to achieve the purposes of that treaty, and that is as important, if not more so, than the need for the rules to be in written form.

Accordingly, this study, which aims to articulate the existing customary rules on the subject, can only help improve respect for international humanitarian law and offer greater protection to victims of war. Knowledge of the relevant customary law on the part of the various actors involved in its application, dissemination and enforcement, such as military personnel, governmental authorities, courts and tribunals and governmental and non-governmental organisations, is a vital first step towards enhancing the effectiveness of international humanitarian law. This study is an invaluable contribution to that goal.

FOREWORD BY DR. YVES SANDOZ
Member of the International Committee of the Red Cross;  former Director of the ICRC Department of International Law  and Policy; Lecturer, Universities of Geneva and Fribourg

The decision to go ahead with a study on customary international humanitarian law depended primarily on the answer to two questions – how useful it would be and how much it would cost – which together give us the famous cost-effectiveness ratio, something that must be taken into account in any undertaking, even if its purpose is humanitarian.

To be sure, applying the criterion of cost-effectiveness is not necessarily appropriate for humanitarian work since it would be cynical to attach a financial price to life and well-being. Nevertheless, those who run an organisation like the ICRC have a moral duty to seek maximum efficiency in the use to which they put their human and financial resources (while seeking to increase those resources). For, as long as there are wars, it will never be possible to do enough, or to do it well enough, to protect and assist those affected.

The international community has given the ICRC the onerous mandate to “work for the faithful application of international humanitarian law”. This imposes a duty of constant vigilance. For the ICRC, impartiality means not only avoiding discrimination between the different victims of a given conflict, but also constantly striving to ensure that all the victims of all the conflicts on the planet are treated equitably, without regional or ethnic preference and independently of the emotions sparked by media-selected images.

This concern to avoid discrimination and to ensure impartiality on a global scale guides the ICRC in choosing its activities. When the time comes to make these choices, meeting the victims’ urgent need for food and medical care logically remains the priority and claims far and away the largest part of the organisation’s budget. How could paying for a meeting of experts take precedence over delivering sacks of flour?

The choices, however, are not that stark. Experience has shown that nothing is to be gained by swinging blindly into action when the fighting starts. Many organisations have learned the hard way that you cannot be effective without first understanding the situation in which you are working, the mentality of those involved in the conflict and the society and culture of those you seek to aid. And if you must first understand, you must also be understood, not only by the combatants – who must know and accept the red cross and red crescent emblems and the principles of humanity, impartiality and neutrality symbolised by that emblem – but also by your intended beneficiaries.

The ICRC’s long experience has convinced it that in order to be effective it has to engage in a wide range of activities, activities that must not be viewed in isolation but rather in relation to one another. The complementary nature of those activities has grown ever clearer with the passing years.

Each of these activities is linked to other activities, all fitting together to form a coherent edifice. That is, humanitarian action in the field prompts discussion, which then develops in meetings of experts of various kinds before eventually taking the form of treaty provisions or new international institutions such as the International Criminal Court, whose Statute was adopted in 1998. The next task is to work towards universal acceptance of the new rules by convincing the States through their governments, their parliaments, their senior officials, etc. of the importance of respecting such rules. Lastly, individual States must be encouraged to adopt national laws incorporating the new rules into domestic legislation, to ensure that the public knows and understands basic humanitarian principles, to ensure that international humanitarian law is adequately taught in schools and universities, and to integrate the subject into military training. The ultimate goal of all this work is to benefit the victims of war and facilitate the task of those seeking to help them.

But it will never be enough. War will remain cruel and there will never be adequate compliance with rules aimed at curbing that cruelty. New problems will arise requiring new forms of action and new discussion about the adequacy of existing rules or their application to new realities. And so the great wheel of law and humanitarian endeavour will continue to turn in the direction of a goal that may never be fully attained, that is, an end to armed conflict. Indeed, that goal sometimes seems to recede amid the pain and anguish of countless wars; but we must always struggle back towards it.

A lawyer in an office working on the development of international humanitarian law is doing a job different from that of the surgeon treating wounded people or a nutritionist in a refugee camp. But all three are in fact pursuing the same objective, each with his or her own place in the indispensable circle of law and humanitarian action.

Ascertaining the role played by legal experts is nevertheless not enough to justify a study on customary international humanitarian law. As part of the process outlined above, the ICRC has in recent years devoted significant resources to considering the state of the law and to spreading knowledge of it. But those resources are limited and choices must therefore be made between various options within the legal domain. Should priority be given to developing new law, promoting national legislation, clarifying certain aspects of practical implementation, consulting experts on sensitive questions, training the miliitary or mobilising public opinion as a means of bringing about greater compliance? All these activities are necessary to some extent, but the question is where the priority belongs. The singular thing about the proposed study on customary law was that it was ill-suited to compromise and to half-measures. The choice was between doing it – and ensuring that one had the means to do it well – and foregoing it on the grounds that its value would rely totally on its credibility.

The decision was eventually taken to go ahead with the project. The ICRC’s Legal Division was assigned this difficult task and given the means to do a thorough job. Lavish means were not necessary because the ICRC is lucky enough to be able to count on volunteer work by a wide range of the world’s leading experts. And we cannot thank them enough for their generosity and commitment. But the administrative work involved and the tasks of organising meetings and translating a number of texts all obviously cost money, as does tapping the sources, in all corners of the world, on which the study is based.

How then can such an investment be justified? Why devote large-scale resources to clarifying what is customary in a branch of law that is so widely codified and by whose treaties the vast majority of States are bound? Many reasons can be given for this, but I will cite two which seem to me essential.

The first is that, despite everything, there remain in international humanitarian law vast but little-known reaches that it is important to explore more fully. This is particularly the case for the rules restricting the use of certain means and methods of warfare. These rules, which were laid down in the Additional Protocols of 1977, very directly concern the military, since it is they who have to implement these rules. If they are sometimes rather vague, this is because at the time of their adoption it was not possible for everyone to agree on a more precise formulation.

The problem is all the more sensitive as the great majority of modern-day armed conflicts are internal, while most of the rules in question are formally applicable only to international conflicts. For the average person, this is completely absurd. Indeed, how can one claim the right to employ against one’s own population means of warfare which one has prohibited for use against an invader? Nevertheless, for historical reasons, precisely this distinction has been made. To be sure, treaties drawn up today tend to soften the effects of this distinction. It exists all the same, and the study on customary law makes it possible to ascertain the extent to which it has been blurred in practice and according to the opinio juris of the States.

The ICRC study also represents an excellent opportunity to view international humanitarian law in its entirety, asking what purpose it has served and how it has been applied, studying the relevance of its various provisions and determining whether some of the problems encountered today do not call for a fresh look at this or that provision.

The study plays a capital role in answering these questions, especially as the problem is not to know whether given rules exist or not but rather how to interpret them. But this is no easy matter. Whatever else, the study’s conclusions will serve as a valuable basis for identifying areas in the law that should be clarified or developed and for engaging in whatever dialogue or negotiation is necessary to strengthen the coherence of military doctrines and those of the jurisprudence of national and international courts, present or future. Therefore, coherence is indispensable to international humanitarian law’s credibility.

The second reason is to be found not so much in the results of the study but in the study itself. Doing research throughout the world to find out how the rules are complied with, translated, taught and applied, then collating that information in order to ascertain both the successes and the remaining gaps – is all this not the best way to ensure more effective application of these rules, to stimulate interest, research and new ideas and, above all, to encourage dialogue between the world’s different cultures? This undertaking has particular significance at a time of renewed tension for humanity when religious and cultural frictions are being exploited for violent ends. The Geneva Conventions have been universally embraced. The rules of international humanitarian law represent a kind of common heritage of mankind, with its roots in all human cultures. They can therefore be viewed as a cement between different cultures. It is thus essential to remind people of those rules and persuade them to comply. The study has been a golden opportunity to do this.

With the fruit of this enormous labour before us, one might think that the circle has been closed. The contrary is the case, however, and I would like to conclude by stressing that this study will have achieved its goal only if it is considered not as the end of a process but as a beginning. It reveals what has been accomplished but also what remains unclear and what remains to be done.

The study is a still photograph of reality, taken with great concern for absolute honesty, that is, without trying to make the law say what one wishes it would say. I am convinced that this is what lends the study international credibility. But though it represents the truest possible reflection of reality, the study makes no claim to be the final word. It is not all-encompassing – choices had to be made – and no one is infallible. In the introduction to De jure belli ac pacis, Grotius says this to his readers: “I beg and adjure all those into whose hands this work shall come, that they assume towards me the same liberty which I have assumed in passing upon the opinions and writings of others.” What better way to express the objective of those who carried out this study? May it be read, discussed and commented on. May it prompt renewed examination of international humanitarian law and of the means of bringing about greater compliance and of developing the law. Perhaps it could even help go beyond the subject of war and spur us to think about the value of the principles on which the law is based in order to build universal peace – the utopian imperative – in the century on which we have now embarked.

The study on customary international humanitarian law is more than the record of a worthy project – it is above all a challenge for the future.

ACKNOWLEDGEMENTS

The realisation of this study would not have been possible without the hard work and commitment of many. Persons from all corners of the globe and with different areas of expertise contributed to the study in the form of research, drafting, reviewing, fact-checking, editing, proofreading and expert advice. We are profoundly grateful to all of them for their dedication, support and assistance. While we have attempted to list each person individually, we are conscious there are also many unnamed persons who have helped in the accomplishment of this work. To all of them, we would also like to express our sincere gratitude and apologise in advance for any inadvertent omissions.

National Research Teams

The reports on State practice were prepared by the following teams:

Algeria:	Professor Ahmed Laraba
Angola:	Professor Maurice Kamto, with the assistance of Albert Hilaire Anoubon Momo and André Ndomikolayi
Argentina:	Professor Raúl Emilio Vinuesa, with the assistance of Silvina Sandra Gonzalez Napolitano and Marta María Pastor
Australia:	Professor Timothy McCormack, with the assistance of Gideon Boas, Malcolm Langford, Colin Andrew Hatcher, Virginia Newell and Shahyar Rousha
Belgium:	Professor Eric David, with the assistance of Isabelle Kuntziger, Garlone Egels and Robert Remacle The financial contribution of the Belgian Red Cross is gratefully acknow- ledged.
Bosnia and Herzegovina:	Colonel Mugo Geć (Federation of Bosnia and Herzegovina) and Professor Liljana Mijović, with the assistance of Nedeljko Milijević (Republika Srpska)
Botswana:	Professor Oagile Key Dingake
Brazil:	Professor Antônio Augusto Cançado Trindade
Canada:	Professor Katia Boustany (deceased), with the assistance of Maria Molina
Chile:	Professor Hernán Salinas Burgos, with the assistance of Daniela Kravetz
China:	Professor Tieya Wang (deceased), with the assistance of Professor Yong Zhang
Colombia:	Fabricio López Sacconi, with the assistance of Raúl Hernández, Magaly Ramos, Sonia Torres and Mauricio Reyes
Croatia:	Professor Maja Seršić, with the assistance of Professor Ksenija Turković, Davorin Lapas and Ivica Kinder
Cuba:	Doctora María de los Angeles de Varona Hernández
Egypt:	Professor Ahmed Abou El Wafa
El Salvador:	Professor Antônio Augusto Cançado Trindade, with the assistance of Cristina Zeledon
Ethiopia:	Professor Andreas Eshete, with the assistance of Alemu Brook
France:	Professor Paul Tavernier, with the assistance of Eloi Fillion, Claire Servoin, Karine Mollard-Bannelier, Davide Ferrarini, Dr. Béatrice Maurer, Karine Christakis, Isabelle Capette, François Darribehaude, Sonia Parayre and Marianne Saracco
Germany:	Professor Horst Fischer, with the assistance of Dr. Gregor Schotten and Dr. Heike Spieker
India:	Professor Nripendra Lal Mitra, with the assistance of Dr. Umesh Veeresh Kadam (research coordinator), Dr. M. K. Nawaz, Dr. S. V. Joga Rao, Dr. V. Vijaya Kumar, M. K. Balachandran, T. S. Matilal and Rekha Chaturvedi
Indonesia:	Professor G. P. H. Haryomataram, with the assistance of Fadillah Agus, Kushartoyo Budisantoso, Arlina Permanasari, Andrey Sujatmoko and Aji Wibowo
Iran:	Professor Djamchid Momtaz, with the assistance of Farah Rahmani
Iraq:	Professor Mohammed Abdallah Ad-Douri, with the assistance of Dr. Janan Sukker
Israel:	Professor Yoram Dinstein, with the assistance of Dr. Fania Domb
Italy:	Professor Gabriella Venturini, Professor Paolo Benvenuti, with the assistance of Dr. Enrico Casalini and Dr. Marco Graziani
Japan:	Professor Hisakazu Fujita, with the assistance of Professor Akira Mayama, Yukiko Takashiba and Hiromi Yoshino
Jordan:	Professor Mohamed Yousef Olwan, with the assistance of Lieutenant-Colonel Muhannad Hijazi and Dr. Ghazi Ar-Rashdan
Korea (Republic of):	Professor Jae-Ho Sung, with the assistance of Dr. Min-Hyo Lee
Kuwait:	Professor Eisa Al-Enezi
Lebanon:	Professor Hassan Kassem Jouni, with the assistance of George Khalil Saad and Abdelrahman Makki
Malaysia:	Professor Nurhalida binti Mohamed Khalil, with the assistance of Zalina binti Abdul Halim
Netherlands:	Anna Nuiten, under the supervision of Dr. Gerard Tanja, Professor Frits Kalshoven, Hans Boddens Hosang, Katrien Coppens, Dr. Liesbeth Lijnzaad and Hanneke van Sambeek The financial contribution of the T. M. C. Asser Institute is gratefully acknowledged.
Nicaragua:	Professor Antônio Augusto Cançado Trindade, with the assistance of Cristina Zeledon
Nigeria:	Professor Amechi Uchegbu, with the assistance of Dr. B. O. Okere and Muhammed T. Ladan, Esq.
Pakistan:	Ahmar Bilal Soofi, Esq.
Peru:	Professor Raúl Emilio Vinuesa, with the assistance of Silvina Sandra Gonzalez Napolitano, Marta María Pastor and Yesenia J. Cabezas Anicama
Philippines:	Professor Alberto T. Muyot, with the assistance of Joel P. Raquedan and Vincent Pepito F. Yambao, Jr.
Russian Federation:	Professor Igor Pavlovitch Blishchenko (deceased), with the assistance of Professor Aslan Abashidze
Rwanda:	Professor Félicité Karomba, with the assistance of Straton Nsengiyumva
South Africa:	Professor Michael Cowling
Spain:	Dr. José Luis Rodríguez-Villasante y Prieto, with the assistance of Manuel Fernández Gómez, Professor Dr. Julio Jorge Urbina, Juan Manuel García Labajo, Juan Carlos González Barral, Vicente Otero Solana, Dr. Gonzalo Jar Couselo, David Suárez Leoz, Dr. Francisco Alonso Pérez, Sonia Hernández Prada, Professor Dr. Manuel Pérez González, Fernando Pignatelli Meca, Javier Guisández Gómez and Federico Bordas
Syria:	Professor Muhammad Aziz Shukri, with the assistance of Dr. Amal Yaziji and Maan Mahasen
United Kingdom:	Professor Françoise Hampson, with the assistance of Dr. Jenny Kuper. The financial contributions of the British Red Cross and the Foreign and Commonwealth Office are gratefully acknowledged.
United States of America:	Burrus M. Carnahan, with the assistance of Michael H. Hoffman and Professor Theodor Meron
Uruguay:	Professor Raúl Emilio Vinuesa, with the assistance of Silvina Sandra Gonzalez Napolitano and Marta Maria Pastor
Yugoslavia:	Professor Milan Šahović, with the assistance of Dejan Šahović, Dr. Miodrag Starčević and Dr. Bosko Jakovljević
Zimbabwe:	Professor Joel Zowa, with the assistance of Dr. Lovemore Madhuku

International Research Teams

The international research teams collected practice from international sources, consolidated their research with those of the national research teams and prepared the first draft of the study. The researchers are Richard Desgagné, Camille Giffard, Gustaf Lind, Gregor Schotten, Heike Spieker and Jean-François Quéguiner.

These researchers worked under the supervision of the Rapporteurs who presented a first assessment of customary international humanitarian law at the meetings of the Steering Committee and a second assessment during the consultations with academic and governmental experts. The Rapporteurs are Professors Georges Abi-Saab, Ove Bring, Eric David, Horst Fischer, Françoise Hampson and Theodor Meron.

The financial contributions of the British and Swedish Red Cross Societies and of the Swedish Ministry of Foreign Affairs towards the work of Professors Hampson and Bring respectively are gratefully acknowledged.

Steering Committee

The study was carried out under the guidance and with the advice of the Steering Committee, whose members are Professors Georges Abi-Saab, Salah El-Din Amer, Ove Bring, Eric David, John Dugard, Florentino Feliciano, Horst Fischer, Françoise Hampson, Theodor Meron, Djamchid Momtaz, Milan Šahović and Raúl Emilio Vinuesa.

Academic and Governmental Experts

The experts invited to comment on the first assessment provided by the international research teams are Abdallah Ad-Douri, Paul Berman, Sadi Çaycý, Michael Cowling, Edward Cummings, Antonio de Icaza, Yoram Dinstein, Jean-Michel Favre, William Fenrick, Dieter Fleck, Juan Carlos Gómez Ramírez, Jamshed A. Hamid, Arturo Hernández-Basave, Ibrahim Idriss, Hassan Kassem Jouni, Kenneth Keith, Githu Muigai, Rein Müllerson, Bara Niang, Mohamed Olwan, Raul C. Pangalangan, Stelios Perrakis, Paulo Sergio Pinheiro, Arpád Prandler, Pemmaraju Sreenivasa Rao, Camilo Reyes Rodríguez, Itse E. Sagay, Harold Sandoval, Somboon Sangianbut, Marat A. Sarsembayev, Muhammad Aziz Shukri, Parlaungan Sihombing, Geoffrey James Skillen, Guoshun Sun, Bakhtyar Tuzmukhamedov and Karol Wolfke.

ICRC Research Team

Numerous persons at the ICRC have worked on the study doing research, checking information and providing editorial assistance, in particular for Volume II. Etienne Antheunissens and Tudor Hera carried out research into the ICRC archives. Carolin Alvermann, Sarah Avrillaud, Gilles Benedick, Joanna Bourke-Martignioni, Angela Cotroneo, Eloi Fillion, Emanuela-Chiara Gillard, Neal Gilmore, Antoine Grand, Valérie Houetz, David Kootz, Carine Nassif, Anna Nuiten, Aurélie Legrand, François Moreillon, Stéphane Ojeda, Guilhem Ravier, Baptiste Rolle, Ion Smochina, Nadine Thwaites, Huyghen van den Eertwegh and Barbara Van der Beken contributed to the final version of Volume II during different stages of the long writing process. In so doing, they benefited from the assistance of Laila Bahaa-el-Din, Namuezi Fedi, Tristan Ferraro, Marie-Eve Friedrich, Francisco-Javier Leon-Diaz and Nathalie Stadelmann and from numerous ICRC staff members in the field who provided additional information on national legislation and case-law. Jérémie Labbe Grenier, Yasmine Hadjoudj, Haleh Mehran and Tobias Schaffner completed the final arduous task of checking the footnotes of Volume I. All these people amply deserve a heartfelt “thank you”.

Research would not have been possible without the assistance of Monica Cometti, Magalie Develon, Florence Gaspar, Brigitte Gremaud and Jean Perrenoud at the ICRC Information and Documentation Center, as well as all the staff at the UN Library in Geneva, in particular Werner Simon, and Jan Hladík at UNESCO Headquarters in Paris.

In addition, we would like to thank Patricia Barbey, Lydie Beguelin, Vojislava Bursac, Renée Bretton, Séverine Mueller-Moine, Christine Pellaton, Janine Rossier, Elodie Straub, Sandrine Wagner and Nina Zufferey for providing indispensable administrative support.

We are also very grateful to all our colleagues, and former colleagues, at the ICRC who so generously gave of their time to review the drafts of Volume I and who provided many insightful comments, including Raoul Bittel, Serge Bourgeois, Laurent Colassis, Isabelle Daoust, Marie-José d’Aprikle, Richard Desgagné, Annemarie Dick, Knut Dörmann, María Teresa Dutli, Alexandre Faite, Emanuela-Chiara Gillard, Thomas Graditzky, Paul Hardy, Peter Herby, Rikke Ish⊘y, Bertrand Levrat, Charlotte Lindsey-Curtet, Barbara Jaeggi, Isabelle Kuntziger, Jean-Philippe Lavoyer, Kathleen Lawand, Dominique Loye, Louis Maresca, Nils Melzer, Laura Olson, Jelena Pejic, Cristina Pellandini, Gabor Rona, Anne Ryniker, Silvia Schaller, Anna Segall, Philip Spoerri, Sylvie van Lammeren and Ameur Zemmali.

A very special word of thanks is due to Knut Dörmann, Emanuela-Chiara Gillard, Laura Olson, Gabor Rona and Jelena Pejic who read and commented on all the drafts and provided invaluable support throughout the writing process.

We owe a special debt of gratitude for the advice and constructive criticism from Maurice Mendelson and Karol Wolfke, who reviewed the introductory part on the assessment of customary international law, and from Sadi Çaycy, Edward Cummings, Eric David, Yoram Dinstein, William Fenrick, Dieter Fleck, Juan Carlos Gómez Ramírez, Michael Meyer, Theodor Meron, Raul Pangalangan, Peter Rowe, Milan Šahović, Marat Sarsembaev, Helen Upton, Elizabeth Wilmshurst and Karol Wolfke for their comments on different drafts of Volume I and Jan Hladík at UNESCO for reviewing the draft chapter on cultural property.

Special thanks are also due to Knut Dörmann, Horst Fischer, Theodor Meron, the Mines and Arms Unit of the ICRC led by Peter Herby, William Fenrick and Antonio Cassese for reviewing Parts I–Ⅵ of Volumes I and II respectively.

The authors express their genuine appreciation to François Bugnion, Jean-Philippe Lavoyer and Yves Sandoz for their advice, comments and support throughout the genesis of this study.

Lastly our sincere gratitude goes to Christina Grisewood for the monumental task of copy-editing both Volumes I and II, to Philippa Youngman, who prepared the copy for typesetting, and the staff at Cambridge University Press, in particular Finola O’Sullivan for supervising publication and Neil de Cort and Alison Powell for overseeing the production.

This study would not have been possible without the patience, support and encouragement of Mei and Josef.

Geneva, August 2004
Jean-Marie Henckaerts
Louise Doswald-Beck

INTRODUCTION

   International humanitarian law has its origins in the customary practices of armies as they developed over the ages and on all continents. The “laws and customs of war”, as this branch of international law has traditionally been called, was not applied by all armies, and not necessarily vis-à-vis all enemies, nor were all the rules the same. However, the pattern that could typically be found was restraint of behaviour vis-à-vis combatants and civilians, primarily based on the concept of the soldier’s honour. The content of the rules generally included the prohibition of behaviour that was considered unnecessarily cruel or dishonourable, and was not only developed by the armies themselves, but was also influenced by the writings of religious leaders.

   The most significant landmark from the point of view of cataloguing these customs in one document was the drafting by Professor Francis Lieber of the Instructions for the Government of Armies of the United States in the Field, promulgated as General Order No. 100 by President Lincoln in 1863 during the American Civil War. The Lieber Code, as it is now known, strongly influenced the further codification of the laws and customs of war and the adoption of similar regulations by other States. Together, they formed the basis of the draft of an international convention on the laws and customs of war presented to the Brussels Conference in 1874. Although this conference did not adopt a binding treaty, much of its work was later used in the development of the 1899 and 1907 Hague Conventions and Declarations. These treaties did not codify all aspects of custom, but its continued importance was reaffirmed in the so-called “Martens clause”, first inserted in the preamble to the 1899 Hague Convention (II), which provides that:

Until a more complete code of the laws of war is issued, the High Contracting Parties think it right to declare that in cases not included in the Regulations adopted by them, populations and belligerents remain under the protection and empire of the principles of international law, as they result from the usages established between civilized nations, from the laws of humanity and the requirements of the public conscience.

   The importance attributed to customary law, despite, or because of, its partial codification, was most clearly seen in the reliance placed on it by the various war crimes trials after both the First and Second World Wars.

   The driving force behind the development of international humanitarian law has been the International Committee of the Red Cross (ICRC), founded in 1863. It initiated the process which led to the conclusion of the Geneva Conventions for the protection of the victims of war of 1864, 1906, 1929 and 1949. It was at the origin of the 1899 Hague Convention (Ⅲ) and 1907 Hague Convention (X), which adapted, respectively, the 1864 and 1906 Geneva Conventions to maritime warfare and were the precursors of the Geneva Convention for the Amelioration of the Condition of the Wounded, Sick and Shipwrecked Members of Armed Forces at Sea of 1949. It took the initiative to supplement the Geneva Conventions that led to the adoption in 1977 of two Additional Protocols. The ICRC has both encouraged the development of and been involved in the negotiation of numerous other treaties, such as the 1980 Convention on Certain Conventional Weapons, the 1997 Ottawa Convention banning anti-personnel landmines and the 1998 Statute of the International Criminal Court. Recognition of this role is reflected in the mandate given to the ICRC by the international community to work for “the faithful application of international humanitarian law applicable in armed conflicts” and for “the understanding and dissemination of knowledge of international humanitarian law applicable in armed conflicts and to prepare any development thereof”.

   More than 50 years have now passed since the Geneva Conventions of 1949 were adopted and almost 30 years since the adoption of their Additional Protocols. These years have, unfortunately, been marked by a proliferation of armed conflicts affecting every continent. Throughout these conflicts, the Geneva Conventions – and in particular Article 3 common to the four Conventions, applicable in non-international armed conflicts – together with their Additional Protocols have provided legal protection to war victims, namely persons who do not or no longer participate in hostilities (the wounded, sick and shipwrecked, persons deprived of their liberty for reasons related to the conflict, and civilians). Nevertheless, there have been countless violations of these treaties and of basic humanitarian principles, resulting in suffering and death which might have been avoided had international humanitarian law been respected.

   The general opinion is that violations of international humanitarian law are not due to the inadequacy of its rules, but rather to a lack of willingness to respect them, to a lack of means to enforce them and to uncertainty as to their application in some circumstances, but also to ignorance of the rules on the part of political leaders, commanders, combatants and the general public.

   The International Conference for the Protection of War Victims, convened in Geneva from 30 August to 1 September 1993, discussed, in particular, ways and means to address violations of international humanitarian law but did not propose the adoption of new treaty provisions. Instead, in its Final Declaration, adopted by consensus, the Conference reaffirmed “the necessity to make the implementation of humanitarian law more effective” and called upon the Swiss government “to convene an open-ended intergovernmental group of experts to study practical means of promoting full respect for and compliance with that law, and to prepare a report for submission to the States and to the next session of the International Conference of the Red Cross and Red Crescent”.

   To this end, the Intergovernmental Group of Experts for the Protection of War Victims met in Geneva in January 1995 and adopted a series of recommendations aimed at enhancing respect for international humanitarian law, in particular by means of preventive measures that would ensure better knowledge and more effective implementation of the law. Recommendation II of the Intergovernmental Group of Experts proposed that:

The ICRC be invited to prepare, with the assistance of experts in IHL [international humanitarian law] representing various geographical regions and different legal systems, and in consultation with experts from governments and international organisations, a report on customary rules of IHL applicable in international and non-international armed conflicts, and to circulate the report to States and competent international bodies.

Purpose of the study

International humanitarian treaty law is well developed and covers a wide variety of aspects of warfare, offering protection to victims of war and limiting permissible means and methods of warfare. The four Geneva Conventions of 1949 and their Additional Protocols of 1977 provide an extensive regime for the protection of persons who do not or no longer participate in armed conflict. The regulation of the means and methods of warfare in treaty law goes back to the 1868 St. Petersburg Declaration, the 1899 and 1907 Hague Conventions and the 1925 Geneva Gas Protocol and has most recently been addressed in the 1972 Biological Weapons Convention, the 1977 Additional Protocols, the 1980 Convention on Certain Conventional Weapons and its five Protocols, the 1993 Chemical Weapons Convention and the 1997 Ottawa Convention banning anti-personnel landmines. The protection of cultural property in the event of armed conflict is regulated in detail in the 1954 Hague Convention and its two Protocols. The 1998 Statute of the International Criminal Court contains a list of war crimes subject to its jurisdiction.

   There are, however, two important impediments to applying these treaties to current armed conflicts. First, treaties apply only to the States that have ratified them. This means that different treaties of international humanitarian law apply to different armed conflicts depending on which treaties the States involved have ratified. While nearly all States have ratified the four Geneva Conventions of 1949, Additional Protocol I has not yet gained universal adherence. As the Protocol is applicable only between parties to a conflict that have ratified it, its efficacy today is limited because several States that have been involved in international armed conflicts are not a party to it. Similarly, Additional Protocol II; is only applicable in armed conflicts taking place on the territory of a State that has ratified it. While some 150 States have ratified this Protocol, several States in which non-international armed conflicts are taking place have not. In these non-international armed conflicts, common Article 3 of the four Geneva Conventions often remains the only applicable treaty provision.

   Secondly, this wealth of treaty law does not regulate a large proportion of today’s armed conflicts in sufficient detail. The primary reason for this is that the majority of current armed conflicts are non-international, which are subject to far fewer treaty rules than international conflicts, although their number is increasing. In fact, only a limited number of treaties apply to non-international armed conflicts, namely the Convention on Certain Conventional Weapons, as amended, the Statute of the International Criminal Court, the Ottawa Convention banning anti-personnel landmines, the Chemical Weapons Convention, the Hague Convention for the Protection of Cultural Property and its Second Protocol and, as already mentioned, Additional Protocol II and Article 3 common to the four Geneva Conventions. While common Article 3 is of fundamental importance, it only provides a rudimentary framework of minimum standards and does not contain much detail. Additional Protocol II usefully supplements common Article 3, but it is still less detailed than the rules governing international armed conflicts contained in Additional Protocol I.

   Additional Protocol II contains a mere 15 substantive articles, whereas Additional Protocol I has more than 80. These figures may not be all important, but they nonetheless show that there is a significant difference in terms of regulation between international and non-international armed conflicts, with the latter suffering from a lack of rules, definitions, details and requirements in treaty law. This is the prevailing situation, even though the majority of armed conflicts today are non-international.

   Specifically, Additional Protocol II contains only a very rudimentary regulation of the conduct of hostilities. Article 13 provides that “the civilian population as such, as well as individual civilians, shall not be the object of attack . . . unless and for such time as they take a direct part in hostilities”. Unlike Additional Protocol I, Additional Protocol II does not contain, however, specific rules and definitions with respect to the principles of distinction and proportionality.

   Common sense would suggest that such rules, and the limits they impose on the way war is waged, should be equally applicable in international and non-international armed conflicts. The fact that in 2001 the Convention on Certain Conventional Weapons was amended to extend its scope to non-international armed conflicts is an indication that this notion is gaining currency within the international community.

   This study provides evidence that many rules of customary international law apply in both international and non-international armed conflicts and shows the extent to which State practice has gone beyond existing treaty law and expanded the rules applicable to non-international armed conflicts. In particular, the gaps in the regulation of the conduct of hostilities in Additional Protocol II have largely been filled through State practice, which has led to the creation of rules parallel to those in Additional Protocol I, but applicable as customary law to non-international armed conflicts.

   Knowledge of the rules of customary international law is therefore of use to the many actors involved in the application, dissemination and enforcement of international humanitarian law, such as governmental authorities, arms bearers, international organisations, components of the International Red Cross and Red Crescent Movement and non-governmental organisations. A study on customary international humanitarian law may also be helpful in reducing the uncertainties and the scope for argument inherent in the concept of customary international law.

   Knowledge of the rules of customary international law may also be of service in a number of situations where reliance on customary international law is required. This is especially relevant for the work of courts and international organisations. Indeed, courts are frequently required to apply customary international law. This is the case, for example, for the International Criminal Tribunal for the Former Yugoslavia which, pursuant to Article 3 of its Statute, has jurisdiction over violations of the laws and customs of war. As a result, the Tribunal has had to determine whether certain violations of international humanitarian law were violations under customary international law over which the Tribunal has jurisdiction. In addition, in many countries, customary international law is a source of domestic law and can be invoked before and adjudicated by national courts. Customary international law is also relevant to the work of international organisations in that it generally represents the law binding upon all member States.

Scope of the study

This study has not sought to determine the customary nature of each treaty rule of international humanitarian law and, as a result, does not necessarily follow the structure of existing treaties. Rather, it has sought to analyse issues in order to establish what rules of customary international law can be found inductively on the basis of State practice in relation to these issues. As the approach chosen does not analyse each treaty provision with a view to establishing whether or not it is customary, it cannot be concluded that any particular treaty rule is not customary merely because it does not appear as such in this study. In this regard, it is important to note that the great majority of the provisions of the Geneva Conventions of 1949, including common Article 3, are considered to be customary law, and the same is true for the 1907 Hague Regulations (see infra). Furthermore, given that the Geneva Conventions have now been ratified by 192 States, they are binding on nearly all States as a matter of treaty law.

   It was decided not to research customary law applicable to naval warfare as this area of law was recently the subject of a major restatement, namely the San Remo Manual on Naval Warfare. The general rules contained in the manual were nevertheless considered useful for the assessment of the customary nature of rules that apply to all types of warfare.

   A number of topics could not be developed in sufficient detail for inclusion in this edition, but they might be included in a future update. These include, for example, the Martens clause, identification of specifically protected persons and objects, and civil defence.

   Where relevant, practice under international human rights law has been included in the study. This was done because international human rights law continues to apply during armed conflicts, as indicated by the express terms of the human rights treaties themselves, although some provisions may, subject to certain conditions, be derogated from in time of public emergency. The continued applicability of human rights law during armed conflict has been confirmed on numerous occasions by the treaty bodies that have analysed State behaviour, including during armed conflict, and by the International Court of Justice (see introduction to Chapter 32). This study does not purport, however, to provide an assessment of customary human rights law. Instead, human rights law has been included in order to support, strengthen and clarify analogous principles of international humanitarian law. In addition, while they remain separate branches of international law, human rights law and international humanitarian law have directly influenced each other, and continue to do so, and this for mainly three reasons. First, an assessment of conformity with human rights law at times involves a determination of respect for or breach of international humanitarian law. For example, measures taken in states of emergency will be unlawful under human rights law if, inter alia, they violate international humanitarian 10law. Conversely, international humanitarian law contains concepts the interpretation of which needs to include a reference to human rights law, for example, the provision that no one may be convicted of a crime other than by a “regularly constituted court affording all the judicial guarantees which are recognised as indispensable”. Secondly, human rights-type provisions are to be found in international humanitarian law, for example, Article 75 of Additional Protocol I and Articles 4 and 6 of Additional Protocol II, and humanitarian law-type provisions are to be found in human rights law, for example, the provisions on child soldiers in the Convention on the Rights of the Child and its Protocol on the Involvement of Children in Armed Conflict. Thirdly, and most significantly, there is extensive practice by States and by international organisations commenting on the behaviour of States during armed conflict in the light of human rights law.

Assessment of customary international law

The Statute of the International Court of Justice describes customary international law as “a general practice accepted as law”. It is generally agreed that the existence of a rule of customary international law requires the presence of two elements, namely State practice (usus) and a belief that such practice is required, prohibited or allowed, depending on the nature of the rule, as a matter of law (opinio juris sive necessitatis). As the International Court of Justice stated in the Continental Shelf case: “It is of course axiomatic that the material of customary international law is to be looked for primarily in the actual practice and opinio juris of States.” The exact meaning and content of these two elements has been the subject of much academic writing. The approach taken in this study to determine whether a rule of general customary international law exists is a classic one, set out by the International Court of Justice in a number of cases, in particular in the North Sea Continental Shelf cases.

State practice

In the assessment of State practice, two separate issues need to be addressed, namely the selection of practice that contributes to the creation of customary international law and the assessment of whether this practice establishes a rule of customary international law.

Selection of State practice

The practice collected for the purpose of this study, and which is summarised in Volume II, was selected on the basis of the following criteria.

   (i) Both physical and verbal acts of States constitute practice that contributes to the creation of customary international law. Physical acts include, for example, battlefield behaviour, the use of certain weapons and the treatment provided to different categories of persons. Verbal acts include military manuals, national legislation, national case-law, instructions to armed and security forces, military communiqués during war, diplomatic protests, opinions of official legal advisers, comments by governments on draft treaties, executive decisions and regulations, pleadings before international tribunals, statements in international organisations and at international conferences and government positions taken with respect to resolutions of international organisations.

   The approach to consider both physical and verbal acts as practice follows that taken by leading bodies in the field of international law and by States themselves. The International Court of Justice has taken into consideration official statements as State practice in a number of cases, including the  Fisheries Jurisdiction cases, the Nicaragua case, and the Gabčíkovo-Nagymaros Project case.

   The International Law Commission has similarly considered verbal acts of States as contributing towards the creation of customary international law. It did so, for example, in the context of the Draft Articles on State Responsibility where it considered the concept of a “state of necessity” to be customary.

   The International Criminal Tribunal for the Former Yugoslavia has stated that in appraising the formation of customary rules of international humanitarian law, “reliance must primarily be placed on such elements as official pronouncements of States, military manuals and judicial decisions”.

   The International Law Association considers that “verbal acts, and not only physical acts, of States count as State practice” and points out that “the practice of the international tribunals is replete with examples of verbal acts being treated as examples of practice. Similarly, States regularly treat this sort of act in the same way.”

   Whether physical or verbal, relevant practice only consists of official practice. Hence, the physical acts of parties to armed conflicts contribute only to the creation of rules of customary international law as long as they represent official practice.

   Abstention from certain conduct is also noted where relevant. Such omissions will be discussed in more detail below.

   (ⅱ) The practice of the executive, legislative and judicial organs of a State can contribute to the formation of customary international law. The State comprises the executive, legislative and judicial branches of government. The organs of these branches can engage the international responsibility of the State and adopt positions that affect its international relations. In case of conflict between the positions of various organs of a State, the practice is considered internally inconsistent and does not contribute to the formation of customary law.

   (ⅲ) Acts do not contribute to the formation of customary international law if they are never disclosed. This is so as long as such acts are not known to other States and, consequently, do not give them an opportunity, if they so wished, to react to them. In order to count, practice has to be public or communicated to some extent. This does not necessarily mean that the practice has to be published or communicated to the whole world, but at least it should be communicated to one other State or relevant international organisation, including the ICRC. States communicate with the ICRC in the context of its international mandate to assist in the implementation of international humanitarian law and the fact that it may “take cognizance of any complaints based on alleged breaches of [international humanitarian law]”.Hence, communications to the ICRC, while often confidential, are not purely private acts and count as State practice.

   (ⅳ) Although decisions of international courts are subsidiary sources of international law, they do not constitute State practice. This is because, unlike national courts, international courts are not State organs. Their decisions have nevertheless been included because a finding by an international court that a rule of customary international law exists constitutes persuasive evidence to that effect. In addition, because of the precedential value of their decisions, international courts can also contribute to the emergence of a rule of customary international law by influencing the subsequent practice of States and international organisations.

   What States claim before international courts, however, is clearly a form of State practice.

   (ⅴ) International organisations have international legal personality and can participate in international relations in their own capacity, independently of their member States. In this respect, their practice can contribute to the formation of customary international law. Therefore, this study has included, for example, the UN Secretary-General’s Bulletin on observance by United Nations forces of international humanitarian law as relevant practice, in particular because “the instructions in the Bulletin reflect the quintessential and most fundamental principles of the laws and customs of war”, even though it is recognised that “the Secretary-General did not consider himself necessarily constrained by the customary international law provisions of the Conventions and Protocols as the lowest common denominator by which all national contingents would otherwise be bound”.

   In addition, official ICRC statements, in particular appeals and memoranda on respect for international humanitarian law, have been included as relevant practice because the ICRC has international legal personality. The practice of the organisation is particularly relevant in that it has received an official mandate from States “to work for the faithful application of international humanitarian law applicable in armed conflicts and  . . . to prepare any development thereof”. The view that ICRC practice counts is also adopted by the International Criminal Tribunal for the Former Yugoslavia, which has regarded the organisation’s practice as an important factor in the emergence of customary rules applicable to non-international armed conflicts. In addition, the official reactions which ICRC statements elicit are State practice.

   (ⅵ) The negotiation and adoption of resolutions by international organisations or conferences, together with the explanations of vote, are acts of the States involved. With a few exceptions, it is recognised that resolutions are normally not binding in themselves and therefore the value accorded to any particular resolution depends on its content, its degree of acceptance and the consistency of State practice outside it. The greater the support for the resolution, the more importance it is to be accorded. Information on reasons for abstentions or negative votes is therefore indicated in this study where relevant, for such votes are often based on disagreement with certain parts of the resolution and not necessarily with the resolution as a whole. Likewise, statements made by States during debates on the drafting of resolutions constitute State practice and have been included where relevant.

   (ⅶ) The practice of armed opposition groups, such as codes of conduct, commitments made to observe certain rules of international humanitarian law and other statements, does not constitute State practice as such. While such practice may contain evidence of the acceptance of certain rules in non-international armed conflicts, its legal significance is unclear and it has therefore been listed under “Other Practice” in Volume II.

Assessment of State practice

State practice has to be weighed to assess whether it is sufficiently “dense” to create a rule of customary international law. To establish a rule of customary international law, State practice has to be virtually uniform, extensive and representative. Although some time will normally elapse before there is sufficient practice to satisfy these criteria, no precise amount of time is required. As stated by the International Court of Justice in the North Sea Continental Shelf cases:

Although the passage of only a short period of time is not necessarily, or of itself, a bar to the formation of a new rule of customary international law on the basis of what was originally a purely conventional rule, an indispensable requirement would be that within the period in question, short though it might be, State practice, including that of States whose interests are specially affected, should have been both extensive and virtually uniform in the sense of the provision invoked; and should moreover have occurred in such a way as to show a general recognition that a rule of law or legal obligation is involved.

The facts brought to the knowledge of the Court disclose so much uncertainty and contradiction, so much fluctuation and discrepancy in the exercise of diplomatic asylum and in the official views expressed on various occasions, there has been so much inconsistency in the rapid succession of conventions on asylum, ratified by some States and rejected by others, and the practice has been so much influenced by considerations of political expediency in the various cases, that it is not possible to discern in all this any constant and uniform usage, accepted as law.

been adopted by certain States both in their national law and in their treaties and conventions, and although certain arbitral decisions have applied it as between these States, other States have adopted a different limit. Consequently, the ten-mile rule has not acquired the authority of a general rule of international law.

   The jurisprudence of the International Court of Justice shows that contrary practice which, at first sight, appears to undermine the uniformity of the practice concerned, does not prevent the formation of a rule of customary international law as long as this contrary practice is condemned by other States or denied by the government itself and therefore does not represent its official practice. Through such condemnation or denial, the original rule is actually confirmed. The International Court of Justice dealt with such a situation in the Nicaragua case in which it looked at the customary nature of the principles of non-use of force and non-intervention, stating that:

It is not to be expected that in the practice of States the application of the rules in question should have been perfect, in the sense that States should have refrained, with complete consistency, from the use of force or from intervention in each other’s internal affairs. The Court does not consider that, for a rule to be established as customary, the corresponding practice must be in absolute rigorous conformity with the rule. In order to deduce the existence of customary rules, the Court deems it sufficient that the conduct of States should, in general, be consistent with such rules, and that instances of State conduct inconsistent with a given rule should generally have been treated as breaches of that rule, not as indications of the recognition of a new rule. If a State acts in a way prima facie incompatible with a recognized rule, but defends its conduct by appealing to exceptions or justifications contained within the rule itself, then whether or not the State’s conduct is in fact justifiable on that basis, the significance of that attitude is to confirm rather than to weaken the rule.

   This finding is particularly relevant for a number of rules of international humanitarian law where there is overwhelming evidence of verbal State practice supporting a certain rule found alongside repeated evidence of violations of that rule. Where this has been accompanied by excuses or justifications by the actors and/or condemnations by other States, such violations are not of a nature to challenge the existence of the rule in question. States wishing to change an existing rule of customary international law have to do so through their official practice and claim to be acting as of right.

   (ⅱ) The second requirement for a rule of general customary international law to come into existence is that the State practice concerned must be both extensive and representative. It does not, however, need to be universal; a “general” practice suffices. No precise number or percentage of States is required. One reason why it is impossible to put a precise figure on the extent of participation required is that the criterion is in a sense qualitative rather than quantitative. That is to say, it is not simply a question of how many States participate in the practice, but also which States. In the words of the International Court of Justice in the North Sea Continental Shelf cases, the practice must “include that of States whose interests are specially affected”.

   This consideration has two implications: (1) if all “specially affected States” are represented, it is not essential for a majority of States to have actively participated, but they must have at least acquiesced in the practice of “specially affected States”; (2) if “specially affected States” do not accept the practice, it cannot mature into a rule of customary international law, even though unanimity is not required as explained. Who is “specially affected” will vary according to circumstances. Concerning the question of the legality of the use of blinding laser weapons, for example, “specially affected States” include those identified as having been in the process of developing such weapons. In the area of humanitarian aid, States whose population is in need of such aid or States which frequently provide such aid are to be considered “specially affected”. With respect to any rule of international humanitarian law, countries that participated in an armed conflict are “specially affected” when their practice examined for a certain rule was relevant to that armed conflict. Notwithstanding the fact that there are specially affected States in certain areas of international humanitarian law, it is also true that all States have a legal interest in requiring respect for international humanitarian law by other States, even if they are not a party to the conflict (see the commentary to Rule 144). As a result, the practice of all States must be considered, whether or not they are “specially affected” in the strict sense of that term.

   This study has taken no view as to whether it is legally possible to be a “persistent objector” in relation to customary rules of international humanitarian law. Apart from the fact that many authorities believe that this is not possible in the case of rules of jus cogens, there are also authorities that doubt the continued validity of this doctrine. If one accepts that it is legally possible to be a persistent objector, the State concerned must have objected to the emergence of a new norm during its formation and continue to object afterwards; it is not possible to be a “subsequent objector”.

   (ⅲ) The third requirement is related to the time necessary to form a rule of customary international law through the adoption of virtually uniform, extensive and representative practice. As indicated above, while some time will normally elapse before there is sufficient practice to satisfy these criteria, there is no specific time requirement. It is all a question of accumulating a practice of sufficient density, in terms of uniformity, extent and representativeness.

Opinio juris

The second requirement for the existence of a rule of customary international law, opinio juris, relates to the need for the practice to be carried out as of right. The particular form in which the practice and this legal conviction needs to be expressed may well differ depending on whether the rule involved contains a prohibition, an obligation or merely a right to behave in a certain manner.

   Practice establishing the existence of a prohibition, for example, the rule that it is prohibited to declare that no quarter will be given (see Rule 46), includes not only statements that such behaviour is prohibited and condemnations of instances where the prohibited behaviour did take place, possibly combined with justifications or excuses from the criticised State, but also physical practice abstaining from the prohibited behaviour. If the practice largely consists of abstention combined with silence, there will need to be some indication that the abstention is based on a legitimate expectation to that effect from the international community.

   Practice establishing the existence of an obligation, for example, the rule that the wounded and sick must be cared for (see Rule 110), can be found primarily in behaviour in conformity with such a requirement. The fact that it is a legal requirement, rather than one reflecting courtesy or mere comity, can be found by either an expression of the need for such behaviour, or by criticism by other States in the absence of such behaviour. It may also be that, following criticism by other States, the criticised State will explain its abstinence by seeking justification within the rule.

   Practice establishing the existence of a rule that allows a certain conduct, for example, the rule that States have the right to vest universal jurisdiction in their courts over war crimes (see Rule 157), can be found in acts that recognise the right to behave in such a way without actually requiring such behaviour. This will typically take the form of States undertaking such action, together with the absence of protests by other States.

   During work on the study it proved very difficult and largely theoretical to strictly separate elements of practice and legal conviction. More often than not, one and the same act reflects practice and legal conviction. As the International Law Association has pointed out, the International Court of Justice “has not in fact said in so many words that just because there are (allegedly) distinct elements in customary law the same conduct cannot manifest both. It is in fact often difficult or even impossible to disentangle the two elements.” This is particularly so because verbal acts count as State practice and often reflect the legal conviction of the State involved at the same time.

   When there is sufficiently dense practice, an opinio juris is generally contained within that practice and, as a result, it is not usually necessary to demonstrate separately the existence of an opinio juris. Opinio juris plays an important role, however, in certain situations where the practice is ambiguous, in order to decide whether or not that practice counts towards the formation of custom. This is often the case with omissions, when States omit to act or react but it is not clear why. An example of such a situation was analysed by the Permanent Court of International Justice in the Lotus case in which France disputed Turkey’s right to prosecute for a collision on the high seas. France argued that the absence of such prosecutions proved a prohibition under customary international law to prosecute, except by the flag State of the ship on board which the wrongful act took place. The Court, however, disagreed because it was not clear whether other States had abstained from prosecuting because they thought they had no right to do so or because of some other reason, for example, lack of interest or belief that a court of the flag State is a more convenient forum. The Court stated there was no evidence of any “consci- ous[ness] of having a duty to abstain”.

   Another situation of ambiguity was analysed by the International Court of Justice in the North Sea Continental Shelf cases in which Denmark and the Netherlands argued that a customary rule existed requiring a continental shelf to be delimited on the basis of the equidistance principle, inter alia, because a number of States had done so. The Court considered that the basis of the action of those States remained speculative and that no inference could be drawn that they believed themselves to be applying a rule of customary international law. In other words, the States that had delimited their continental shelf on the basis of the equidistance principle had behaved in accordance with that principle but nothing showed that they considered themselves bound by it. It is basically in such cases, where practice is ambiguous, that both the International Court of Justice and its predecessor, the Permanent Court of International Justice, have looked in particular at whether they could separately establish the existence of an opinio juris that would indicate that the ambiguous practice in fact counted towards the establishment of customary international law.

   In the area of international humanitarian law, where many rules require abstention from certain conduct, omissions pose a particular problem in the assessment of opinio juris because it has to be proved that the abstention is not a coincidence but based on a legitimate expectation. When such a requirement of abstention is indicated in statements and documents, the existence of a legal requirement to abstain from the conduct in question can usually be proved. In addition, such abstentions may also occur after the behaviour in question created a certain controversy, which also helps to prove that the abstention was not coincidental, although it is not always easy to conclude that the abstention occurred because of a sense of legal obligation. A particular example of this problem is abstention from certain conduct in non-international armed conflicts when a clear rule to abstain from such conduct can only be found in treaty law applicable to international armed conflicts. This is, for example, the case for abstention from the use of certain weapons in non-international armed conflicts, when the prohibition of the use of these weapons was agreed to by treaty a long time ago when rules in relation to non-international armed conflicts were not as readily thought about or accepted as they are now. Abstention from such use or of prohibited behaviour is not likely to lead other States to comment, and this is particularly the case in relation to non-international armed conflicts in which other States are not directly affected. The process of claim and counterclaim does not produce as much clarity with respect to non-international armed conflicts as it does with respect to international armed conflicts because in the latter case, two or more States are directly affected by each other’s behaviour, while in the former case, usually only one State is directly affected.

   It appears that international courts and tribunals on occasion conclude that a rule of customary international law exists when that rule is a desirable one for international peace and security or for the protection of the human person, provided that there is no important contrary opinio juris. Examples of such conclusions are the finding by the International Military Tribunal at Nuremberg that the Hague Conventions of 1907 had hardened into customary law, and the finding by the International Court of Justice in the Nicaragua case that the rule of non-intervention in the internal and external affairs of other States was part of customary international law.However, when there was clear evidence of contrary opinio juris by a number of States, including specially affected ones, international case-law has held that the existence of a rule of customary international was not proven, for example, the advisory opinion of the International Court of Justice in the Nuclear Weapons case on the issue of whether the use of nuclear weapons was illegal, and the ruling of the sole arbitrator in the Texaco ⅴ. Libya case on the issue of a possible change in the law relating to compensation for expropriation.

   This aspect of the assessment of customary law is particularly relevant for international humanitarian law, given that most of this law seeks to regulate behaviour for humanitarian reasons. In some instances, it is not yet possible to find a rule of customary international law even though there is a clear majority practice in favour of the rule and such a rule is very desirable.

Impact of treaty law

Treaties are also relevant in determining the existence of customary international law because they help assess how States view certain rules of international law. Hence, the ratification, interpretation and implementation of a treaty, including reservations and statements of interpretation made upon ratification, are included in the study. In the North Sea Continental Shelf cases, the International Court of Justice clearly considered the degree of ratification of a treaty to be relevant to the assessment of customary law. In that case, the Court stated that “the number of ratifications and accessions so far secured [39] is, though respectable, hardly sufficient”, especially in a context where practice outside the treaty was contradictory.Conversely, in the Nicaragua case, the Court placed a great deal of weight, when assessing the customary status of the non-intervention rule, on the fact that the UN Charter was almost universally ratified and that relevant UN General Assembly resolutions had been widely approved, in particular Resolution 2625 (ⅩⅩⅤ) on friendly relations between States, which was adopted without a vote. It can even be the case that a treaty provision reflects customary law, even though the treaty is not yet in force, provided that there is sufficiently similar practice, including by specially affected States, so that there remains little likelihood of significant opposition to the rule in question.

   In practice, the drafting of treaty norms helps to focus world legal opinion and has an undeniable influence on the subsequent behaviour and legal conviction of States. This reality was recognised by the International Court of Justice in the Continental Shelf case:

   It is of course axiomatic that the material of customary international law is to be looked for primarily in the actual practice and opinio juris of States, even though multilateral conventions may have an important role to play in recording and defining rules deriving from custom, or indeed in developing them.   The Court thus recognised that treaties may codify pre-existing customary international law but may also lay the foundation for the development of new customs based on the norms contained in those treaties. The Court has even gone so far as to state that “it might be that  . . . a very widespread and representative participation in [a] convention might suffice of itself, provided it included that of States whose interests were specially affected”.55

The International Law Association has summarised this case-law, stating that a (multilateral) treaty may thus interact in four different ways with custom: it can provide evidence of existing custom; it can provide the inspiration or model for the adoption of new custom through State practice; it can assist in the so-called “crystallisation” of emerging custom; and it can even give rise to new custom of “its own impact” if the rule concerned is of a fundamentally norm-creating character and is widely adopted by States with a view to creating a new general legal obligation. There can be no presumption that any of these interactions has taken place and in each case it is a matter of examining the evidence.