International organisations, non-State actors, and the formation of customary international law

By Manchester University Press

This volume offers new practical and theoretical perspectives on one of the most complex questions regarding the formation of international law, namely that actors other than states contribute to the making of customary international law.


Notwithstanding the International Law Commission’s valuable contribution, the making of customary international law remains riddled with acute practical and theoretical controversies that continue to be intensively debated. Making extensive reference to the case-law of international law courts and tribunals, as well as the most recent scholarly work on customary international law, this volume provides a comprehensive study of the contribution of international organisations and non-state actors to the formation of customary international law. With innovative tools and guidance for law students, legal scholars, and researchers in law, as well as legal practitioners, advisers, judges, arbitrators, and counsels, this collection is essential reading for those wishing to understand and address contemporary questions of international law-making.

• Language: English
• Publisher: Manchester University Press
• Release date: Dec 8, 2020
• ISBN: 9781526134172

Book preview

International organisations, non-State actors, and the formation of customary international law

Melland Schill Perspectives on International Law

General Editors

Professor Jean d’Aspremont

Dr Sufyan Droubi

Professor Iain Scobbie

Building on the history of Melland Schill Classics and Melland Schill Studies at Manchester University Press, Melland Schill Perspectives on International Law was established to reflect the diversity of international legal scholarship worldwide. This inclusive, accessible series aims to offer a platform for scholars from different regions who adopt innovative approaches to new and old topics.

Melland Schill Perspectives on International Law is founded on the idea that every international legal issue should be debated from various and, at times, incommensurable perspectives. Though there is a great deal of diversity in international legal debates and practice, this diversity is often obfuscated by prevailing Euro-centric and positivist narratives, which not only creates difficulties for non-Western scholars to be heard but hinders the development of different approaches.

International organisations, non-State actors, and the formation of customary international law

Edited by Sufyan Droubi and Jean d’Aspremont

Manchester University Press

Copyright © Manchester University Press 2020

While copyright in the volume as a whole is vested in Manchester University Press, copyright in individual chapters belongs to their respective authors, and no chapter may be reproduced wholly or in part without the express permission in writing of both author and publisher.

Published by Manchester University Press

Altrincham Street, Manchester M1 7JA

www.manchesteruniversitypress.co.uk

British Library Cataloguing-in-Publication Data

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

ISBN 978 1 5261 3415 8 hardback

First published 2020

The publisher has no responsibility for the persistence or accuracy of URLs for any external or third-party internet websites referred to in this book, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate.

Typeset by Newgen Publishing UK

Contents

List of figures

List of tables

Notes on contributors

Introduction: stories about international organisations, non-State actors, and the formation of customary international law – Sufyan Droubi and Jean d’Aspremont

Part I: Theoretical and conceptual perspectives

1International organisations as autonomous actors – Nikolaos Voulgaris

2Capturing the juridical will – Catherine Brölmann

3Opinio juris: between mental states and institutional objects – Sufyan Droubi

4Beyond the either-or paradigm – Lorenzo Gasbarri

5Between anthropomorphism and artificial unity – Maiko Meguro

6Custom as the product of successful argumentative campaigns – Fabian Cardenas

7Unlearning some common tropes – Jean d’Aspremont

Part II: Field perspectives and case studies

8International organizations and non-State actors in the International Law Commission’s conclusions on identification of customary international law – Michael Wood

9The International Law Commission perspective on non-State actors and customary international law – Veronika Bílková

10The International Law Commission in the eyes of the International Law Commission: mirror or looking-glass? – Luíza Leão Soares Pereira

11The riddle of custom: General Assembly resolutions – Rossana Deplano

12The United Nations Secretariat and custom – Jean-Baptiste Merlin

13The making of custom through sanctions of international organisations – Maruša T. Veber

14The International Committee of the Red Cross and custom – Iris Müller

15Treaty bodies and States: shaping custom – Kasey McCall-Smith

16The contribution to customary international law by territories under international administration – William Thomas Worster

17The formation of customary international law by de facto regimes – Antal Berkes

18Investors in the formation of customary international law – Tomoko Yamashita

19Adjudicators, guardians, and enforcers: taking the role of non-governmental organisations in customary international lawmaking seriously – Valentina Azarova

Index

Figures

11.1Resolutions adopted in plenary sessions and individual committees (1946–2016)

11.2Resolutions adopted with or without a vote (1946–2016)

Tables

11.1Example of resolutions adopted by the Fourth Committee (1946–2016)

19.1Effects of non-governmental organisation activity on customary international lawmaking

Contributors

Valentina Azarova is an international legal practitioner and scholar with fifteen years of experience working with and advising non-governmental organisations, focusing on questions of economic and social global inequality including as they result from armed conflict. She is Legal Advisor to the Global Legal Action Network (GLAN). She is also Research Fellow at the Manchester International Law Centre, University of Manchester and Visiting Fellow at the Institute for International Law of Peace and Armed Conflict, Ruhr University, Bochum. Her contribution to this volume is based on her work with civil society in the Middle East and North Africa where she has lived and held academic posts for over a decade, including in Palestine, Lebanon, and Turkey.

Antal Berkes is lecturer in law at Brunel University London. In 2019, he was a postdoctoral research fellow at the SARChI Professorship on International Constitutional Law (Prof Erika de Wet) at the University of Pretoria, where he wrote his book entitled International Human Rights Law in Areas out of the Effective Control of the State (forthcoming). He is visiting scholar at the Manchester International Law Centre, University of Manchester.

Veronika Bílková is an associate professor in International Law at the Faculty of Law of the Charles University in Prague and the head of the Centre for International Law of the Institute of International Relations, Prague. Since 2010, she has represented the Czech Republic in the Venice Commission of the Council of Europe. Since 2018, she has been the Secretary-General of the European Society of International Law (ESIL). Having a background in both law and political science, she combines theoretical research with a more policy-oriented approach. She was the final rapporteur of the ILA Committee on Non-State Actors.

Catherine Brölmann is Associate Professor of International Law at the University of Amsterdam. She is co-editor-in-chief of Oxford International Organizations and an editor on the board of International Community Law Review. She is a member of the Advisory Committee for Public International Law of the Netherlands Government.

Fabian Cardenas is Professor of International Law at the University of Bogota Jorge Tadeo Lozano. He directs the LLM programmes in environmental law and teaches public international law, international legal theory, and international environmental law. He is founder and board member of the Colombian Academy of International Law; member of the interest group on international responsibility and the environment of the Latin American Society of International Law. His books and academic articles primarily concern the theory of the sources of international law, international environmental law, as well as the law of the sea and the operation of the International Criminal Court with regards to Colombia and Latin America. With fifteen years of academic experience, he has also worked as a diplomat and international legal advisor of Colombia and some international organisations.

Jean d’Aspremont is Professor of International Law at Sciences Po School of Law. He also holds a chair of Public International Law at the University of Manchester where he founded the Manchester International Law Centre (MILC). He is General Editor of the Cambridge Studies in International and Comparative Law and Director of Oxford International Organizations (OXIO). He is a member of the Scientific Advisory Board of the European Journal of International Law and series editor of the Melland Schill Studies in International Law.

Rossana Deplano is Lecturer in Law at the University of Leicester. Her main research interests lie in the field of public international law, with a focus on United Nations law, international legal theory, and international legal research. In 2017, her monograph entitled The Strategic Use of International Law by the United Nations Security Council: An Empirical Study (Springer 2015) was noted as one of the five most influential books of the year by the President of the European Society of International Law. She is currently writing a monograph for Cambridge University Press entitled Empirical and Theoretical Approaches to International Law: How States Use the United Nations General Assembly to Create International Obligations. She is also the co-editor of the first Handbook on Research Methods in International Law (Elgar, forthcoming 2020).

Sufyan Droubi is Lecturer in Law within the School of Social Sciences, University of Dundee. Previously, Sufyan was a Research Fellow at the University of São Paulo and at the University of Manchester, sponsored by a FAPESP Postdoctoral Fellowship. He holds a PhD in Law from the University of Essex. A fully qualified lawyer in Brazil since 1996, he spent fifteen years in practice before turning to the academia. He is one of the editors of the Melland Shill Perspectives to International Law; and one of the coordinators of the Interest Group on International Organisations of the European Society of International Law.

Lorenzo Gasbarri is research fellow in international law and visiting lecturer at Bocconi University. He has studied at the University of Florence, Milan and at the Graduate Institute in Geneva. Lorenzo has held research positions at University College London and at the University of Helsinki and has been visiting fellow at the University of Copenhagen and at the Max Planck Institute in Heidelberg. He is junior editor of the Oxford database on international organisations and convener of the interest group on the law of international organisations of the European Society of International Law.

Kasey McCall-Smith is a Senior Lecturer in Public International Law and the Programme Director of the LLM in Human Rights at the University of Edinburgh Law School. She researches and publishes predominantly in the areas of treaty law, corporate social responsibility relating to modern slavery, treaty body jurisprudence, and the domestic incorporation and implementation of human rights treaties. She is currently the Chair of the Association of Human Rights Institutes.

Maiko Meguro is a PhD research fellow of the Amsterdam Centre for International Law, University of Amsterdam. Her research focus is mainly on international lawmaking, particularly on the way decision-making processes at domestic and international levels interact. She also works as a legal officer for DG CNECT (the European Commission) and Ministry of Economy, Trade and Industry of Japan.

Jean-Baptiste Merlin is an associate member of the Centre de droit international de Nanterre (CEDIN) and a consultant in public international law. From October 2015 to the completion of the topic in 2018 he was an assistant of the Special Rapporteur of the United Nations International Law Commission on the topic ‘Identification of customary international law’. A graduate from the Institut d’Etudes Politiques of Aix-en-Provence, France (2010), he holds a PhD in public law from the University of Paris Nanterre (2015). His experience as an international lawyer also includes practice as Counsel representing States in cases before international jurisdictions, including the International Court of Justice and the International Tribunal for the Law of the Sea. He also serves as arbitrator’s collaborator in cases before the International Centre for Settlement of Investment Disputes.

Iris Müller, Legal Adviser, Legal Division, International Committee of the Red Cross.

Luíza Leão Soares Pereira is Lecturer in International Law at the University of Sheffield, UK. She has studied at the University of Cambridge, UK, and at Universidade Federal do Rio Grande do Sul, Brazil. Her research is on the role of individual international lawyers in lawmaking and the functioning of the international legal profession.

Maruša T. Veber is a teaching assistant and a PhD candidate at the Department of International Law at the Faculty of Law, University of Ljubljana. She is pursuing her PhD in collaboration with the Manchester International Law Centre on the topic of sanctions adopted by international organisations in the defence of the general interest. Previously she was a junior visiting fellow at the Graduate Institute of International and Development Studies in Geneva, a visiting scholar at the University of Hull Law School and a researcher at the United Nations University Institute on Comparative Regional Integration Studies (UNU-CRIS) in Bruges. She is a member of Geneva International Sanctions Network and a member of Slovene branch of International Law Association.

Nikolaos Voulgaris is a law lecturer at the European Law & Governance School in Athens and a post-doctoral Fellow at the Athens Public International Law Center. He studied law in Athens (National and Kapodistrian University) and London (King’s College London). He is also teaching assistant at the National and Kapodistrian University and is a non-practising member of the Athens bar.

Michael Wood, 20 Essex Street Chambers, Member of the International Law Commission (Special Rapporteur for Identification of customary international law between 2012 and 2018).

William Thomas Worster is Senior Lecturer in International Law at The Hague University of Applied Sciences where he has taught public international law, international organisations, and international migration and refugee law for more than ten years. Prior to teaching, he served at the International Criminal Tribunal for the former Yugoslavia, and also worked in various countries in private firms, NGOs, and government. He is the author of more than forty articles and book chapters in his fields of expertise, and has also spoken at more than fifty universities and international conferences worldwide.

Tomoko Yamashita is Associate Professor of International Law at Aichi Prefectural University, Japan. She obtained PhD (2015), LLM (2009), and LLB (2007) from Kobe University and Master Complémentaire en droit international (2012) from Université libre de Bruxelles.

Introduction: stories about international organisations, non-State actors, and the formation of customary international law

Sufyan Droubi and Jean d’Aspremont

International lawyers relish telling stories about customary law, its contents, and its modes of ascertainment. There is hardly a question of international law that has continuously attracted as much passionate story-telling as customary international law. The present volume contributes to such scholarly self-indulgence. Yet, it does so by presupposing that there exists an approach to custom-forming that is adverse to the central role of international organisations and non-State actors and which it calls the dominant orthodoxy. According to this projected dominant orthodoxy, the formation of customary international law is reduced to a process through which international actors with full lawmaking capacity – States – adopt practices with the conviction that such practices are required in international law.¹ In such image, international organisations are reduced to agents of States; and their main contribution comes in the form of resolutions, which are relevant to the extent that they reflect practice or opinio juris of States.² International organisations as such, i.e. as autonomous actors, are often taken to have very restricted formal participation in the formation of customary international law – which is often the result of a generally held perception that in most issues international organisations lack volonté distincte.³ At best, this image holds that international organisations and non-State actors may influence the conduct and opinio juris of States, but this only means that their participation is instrumental or merely accidental.⁴ In some variants of this image, the role of non-State actors in custom-formation is even denied on grounds that they lack lawmaking capacity.⁵

Whether such adversity towards international organisations and non-State actors in the formation of customary law constitutes an empirical actuality in the international legal scholarship as a whole is not relevant here. In fact, it does not matter whether most international lawyers actually defend such restricted role of international organisations and non-State actors in the formation of custom. This image and its depiction as the dominant orthodoxy offer a convenient starting point for this discussion attempted in this volume. In particular, this projected dominant orthodoxy provides a sounding board for reflecting anew on the possible ways in which international organisations and non-State actors contribute to the formation of customary law and providing new perspectives to the formation of customary international law. For instance, the presupposed orthodoxy described above is what allows many contributions in this volume to suggest that the process of formation of customary international law should be placed beyond the static, formal rule-making framework – and appreciated in all its full dynamism and complexity. This presupposed orthodoxy also provides the background story against which the following chapters offer a wide range of refreshing and new stories about the role of non-State actors and international organisations in the formation of customary international law.

1 The International Law Commission as the starting point of contemporary stories about customary international law

Although customary international law has continuously been on the agenda of international legal scholars, it seems uncontested that debates and story-telling on custom have been reinvigorated by the work of the International Law Commission on the topic. Indeed, under the rapporteurship of Sir Michael Wood, the work of the International Law Commission has fueled much interest for the question within and outside academic circles. It is noteworthy that Sir Michael has personally encouraged input from academics over the years, and has made ample use of the academic commentary.⁶ As is well-known, the objective of the International Law Commission has always been to produce a set of Conclusions and Commentaries thereto to ‘offer practical guidance on how the existence of rules of customary international law, and their content, are to be determined’.⁷ In the view of the International Law Commission:

This is not only of concern to specialists in public international law: others, including those involved with national courts, are increasingly called upon to identify rules of customary international law. In each case, a structured and careful process of legal analysis and evaluation is required to ensure that a rule of customary international law is properly identified, thus promoting the credibility of the particular determination as well as that of customary international law more broadly.⁸

Whether the Conclusions and Commentaries will succeed in enhancing the ‘process of legal analysis and evaluation’, which a multitude of academics and professionals carry out routinely, so that the identification of a rule of customary international law be ‘properly’ made, is unknown. However, the International Law Commission codification process encapsulates a powerful story,⁹ which has already been affecting the story-telling activities that international lawyers articulate – and one should expect that the Conclusions and Commentaries will have a significant impact on international lawyers’ story-telling. To substantiate this assertion, it is enough to recall that the General Assembly of the United Nations has recently adopted Resolution 203 in which the General Assembly, inter alia:

Welcomes the conclusion of the work of the International Law Commission on identification of customary international law and its adoption of the draft conclusions and commentaries thereto;

… Also takes note of the conclusions on identification of customary international law, the text of which is annexed to the present resolution, with the commentaries thereto, brings them to the attention of States and all who may be called upon to identify rules of customary international law, and encourages their widest possible dissemination.¹⁰

And, taking forward an important recommendation put forward by Sir Michael and the International Law Commission,¹¹ the General Assembly, in the same Resolution 203:

Acknowledges the utility of published digests and surveys of practice relating to international law, including those that make legislative, executive and judicial practice widely available, and encourages States to make every effort to support existing publications and libraries specialized in international law.¹²

In these paragraphs, with these simple but significant actions – welcoming, taking note, and acknowledging – the General Assembly not only strengthened the story that encapsulates the Conclusions and Commentaries – but also made a call for States to continue to tell this story.

This having been said, it is undeniable that the work that Sir Michael and the International Law Commission carried out has already significantly, positively contributed in terms of offering opportunities for international lawyers to reflect upon both the orthodox (proper?) and unorthodox (improper?) approaches to the process of formation and expression of rules of customary international law. Of this, the present volume is evidence enough. On the topics that mostly interest us in this volume – formation of customary international law and the weight to be ascribed to international organisations and non-State actors – the work that Sir Michael and the International Law Commission conducted has shed light on a number of controversies that will be taken up in the following chapters. It suffices here to mention a few of them.

First, the International Law Commission codification enterprise appears to have been affected by differing perceptions by members of the International Law Commission in respect to how much the latter could delve into formation of customary international law without going beyond the scope of its mandate and surrendering to academic exercises.¹³ For his part, Sir Michael was not fully convinced as to the need to address formation in an express manner.¹⁴ Second, these three topics – formation, international organisations, and non-State actors – proved contentious within the International Law Commission. As far as these matters are concerned, the Conclusions and Commentaries only reflect the extent of the agreement that members of the International Law Commission were able to reach.¹⁵

This explains why the International Law Commission did not prove very innovative in respect to such topics, and did not do justice to the different processes and actors that operate in the formation and identification of customary international law and which has long been acknowledged in parts of the scholarship and the international argumentative practice of certain States.¹⁶ This is why, for the sake of this volume, the work of the International Law Commission and of Sir Michael are deemed to represent the orthodoxy which this volume takes as its starting point.¹⁷ Within the strict limits of academic rigour, the following chapters at times support and at times challenge this orthodoxy – as well as the standards of ‘proper’ identification of rules of customary international law that this orthodoxy encapsulates in a coherent and well-told story. This is why the work of the International Law Commission on the formation of customary international law – and the project of dominant orthodoxy that serves as the starting point of this volume – must be sketched out in more detail.

We must begin by recalling that the International Law Commission reaffirms the two-element approach, defining customary international law in terms of ‘general practice accepted as law (opinio juris)’.¹⁸ It attempts to photograph moments in the advanced stages of the processes of formation of customary legal rules, and then to offer the pictures as proofs against which the existence of putative norms may be assessed. This photographing strips the socio-political processes of formation of customary international law of much of their dynamism. For instance, it narrows ‘practice’, which has a dynamic component of continuity or repetition, down to ‘conduct’, which is often related to a particular situation and place.¹⁹ It attempts to clearly distinguish between lex lata and lege ferenda: treaties and resolutions of international organisations, for instance, may either reflect customary international law or contribute to the development of new customary international law,²⁰ avoiding the debate of whether emergent custom in its more mature stage really fits within either category.

Whether or not the position of the International Law Commission will withstand the reality of the process of emergence and identification of customary international law is to be seen. At this stage, it should not be difficult to understand why some of the following chapters contend that the Conclusions and Commentary fail to capture the dynamics of the socio-political processes of formation of customary international law. For these scholars, the Conclusions might fail to address important implications that these processes have in international law. They might fail in providing guidance as to the identification of certain rules of customary international law, and in offering help in the weighting of the role that actors other than the State play in the formation of customary international law. Let us look at these two aspects in turn.

The Conclusions and Commentaries might fail in providing guidance as to the proper identification of new rules of customary international law – rules which have not been clearly affirmed as such in the international practice and which not rarely are identified as ‘emerging’ rules of custom.²¹ What is the weight of an ‘emerging’ rule? Who decides when it has fully ‘crystallised’? When does it ‘crystallise’? Is it really possible to ascertain the ‘crystallisation’ of a rule of customary international law? The metaphor of crystallisation encapsulates the challenges in providing formal standards for the identification of a new rule of customary international law and differentiating it from an emerging custom in its more mature stage. It is curious that the International Law Commission decided to keep the metaphor of ‘crystallisation’,²² after the International Law Association cautioned, though timidly, against it.²³ In its attempt to explain ‘crystallisation’, the Commentary becomes circular:

Subparagraph (b) concerns the case where it is established that a general practice that is accepted as law (accompanied by opinio juris) has crystallized around a treaty rule elaborated on the basis of only a limited amount of State practice. In other words, the treaty rule has consolidated and given further definition to a rule of customary international law that was only emerging at the time when the treaty was being drawn up, thereby later becoming reflective of it. Here, too, establishing that this is indeed the case requires an evaluation of whether the treaty formulation has been accepted as law and does in fact find support in a general practice.²⁴

Interestingly, a very similar criticism was anticipated in the debates within the International Law Commission. In 2012 Shinya Murase noted that the word ‘evidence’, which had been part of the title of the Conclusions, ‘was static and premised on the idea that the law was made up of a body of rules’ and that it ‘meant stopping the clock and trying to ascertain the applicable law at a given moment’.²⁵ In contradistinction, he argued, ‘formation was a dynamic concept which … suggested a sociological process whereby a customary rule was created over a period of time’.²⁶ Murase contended that ‘it was impossible to talk simultaneously of formation and evidence without causing some methodological confusion’.²⁷ Ultimately, the word ‘formation’, initially part of the title, was dropped altogether.²⁸ That said, the Conclusions are less concerned with the formation and more concerned with the identification of customary international law.²⁹ Nevertheless, whether a framework that is developed to identify customary international law should be applied also to ascertain its formation, an aspect that becomes more relevant the younger the rule is, is a point that is open to discussion.³⁰ Notwithstanding the obvious fact that formation and identification remain deeply interlinked, some contributions in this volume clearly suggest that not only it is possible to differentiate between them, but that they should be differentiated so as to grasp their different legal implications.³¹

It should also be recalled here how difficult the specific debates on the very role of international organisations and non-State actors in the formation of customary international law turned out within the International Law Commission.³² According to the approach favoured by the Commission, it is ‘primarily … the practice of States that contributes to the formation, or expression of rules of customary international law’.³³ In respect to international organisations, the most relevant contributions that the Conclusions make consist in the affirmation that ‘[i]‌n certain cases, the practice of international organisations also contributes to the formation, or expression, of rules of customary international law’.³⁴ As one reads the Commentary, one notes that the expression ‘in certain cases’ is critical:

The practice of international organizations in international relations (when accompanied by opinio juris) may count as practice that gives rise or attests to rules of customary international law, but only those rules (a) whose subject matter falls within the mandate of the organizations, and/or (b) that are addressed specifically to them (such as those on their international responsibility or relating to treaties to which international organizations may be parties). The words ‘in certain cases’ in paragraph 2 indeed serve to indicate that the practice of international organizations will not be relevant to the identification of all rules of customary international law, and further that it may be the practice of only some, not all, international organizations that is relevant.³⁵

The principal-agency theory, implicit in the extract above, becomes clear in other parts:

International organizations are not States [!]‌ They are entities established and empowered by States (or by States and/or other international organizations) to carry out certain functions, and to that end have international legal personality, that is, they have their own rights and obligations under international law.

… As a general rule, the more directly a practice of an international organization is carried out on behalf of its member States or endorsed by them, and the larger the number of such member States, the greater weight it may have in relation to the formation, or expression, of rules of customary international law.³⁶

Within this framework, it should be expected that the International Law Commission would, as it in fact did, largely ignore the issue concerning the opinio juris of international organisations, which is mentioned en passant in the Commentary to Conclusion 4(2).³⁷

As the Institute of International Lawyers and the International Law Association have done before, the International Law Commission places particular emphasis on resolutions of international organisations, clearly affirming that resolutions ‘may provide evidence for determining the existence and content of a rule of customary international law, or contribute to its development’.³⁸ Even on this point, however, there is a strong caveat to the effect that ‘a provision in a resolution … may reflect a rule of customary international law if it is established that the provision corresponds to a general practice that is accepted as law (opinio juris)’.³⁹

Interestingly, and unfortunately, the International Law Commission refrained from providing any Conclusion defining its own role in the process of formation and identification of customary international law. The point is however briefly mentioned in the Commentary to Conclusion 10 where it is contended that ‘a determination by the Commission affirming the existence and content of a rule of customary international law may have particular value’ because of the Commission’s ‘unique mandate’, the ‘thoroughness of its procedures’ and its ‘close relationship with the General Assembly and States’ – even in these circumstances, however, the significance of its determinations depends on ‘various factors, including sources relied upon by the Commission, the stage reached in its work and above all upon States’ reception of its output’.⁴⁰

As far as non-State actors are concerned, the Conclusions clearly affirm that their conduct ‘is not practice that contributes to the formation, or expression of’ customary international law, but acknowledge that their ‘conduct may be relevant when assessing the practice’ of States and international organisations.⁴¹ In Commentary to Conclusion 4(3), it is clearly stated, in respect to non-governmental organisations, non-State armed groups, transnational corporations, and private individuals, that their conduct does not qualify as ‘direct (primary) evidence of the existence and content of’ rules of customary international law, but their ‘conduct may have an indirect role in the identification of customary international law, by stimulating or recording the practice and acceptance as law (opinio juris) of States and international organisations’.⁴² The International Committee of the Red Cross is also mentioned, in a separate and brief paragraph, as capable of playing ‘an important role in shaping the practice of States’; while its ‘activities may thus contribute to the development and determination of customary international law; but they are not practice as such’.⁴³ The question that arises is whether one paragraph can summarise the many stories about formation and identification of customary international law, in which non-State actors have been playing increasingly important roles. Several chapters in this volume suggest it does not.

2 The stories of this volume

The work of the International Law Commission, as it has been depicted, has promoted most scholarly debates in the last years, and constitutes the presupposed dominant orthodoxy which most of the following chapters take issue with. These contributions do not only engage with the International Law Commission Conclusions and Commentary but also with the numerous reports and debates produced on this occasion with a view to furthering the academic discussion on the three above-mentioned topics, namely, formation of customary international law and the weight to be ascribed to international organisations and non-State actors. These contributions are organised in two main groups, which form the two parts of this volume. A first group of contributions provides innovative theoretical and conceptual perspectives on the role of international organisations and non-State actors on the formation of customary law. A second group of contributions offer field perspectives and case studies.

The volume begins with a chapter by Voulgaris, who aims at understanding the reasons behind the lack of consensus within International Law Commission on the weight of international organisations in the formation of customary international law and how this has affected outcomes of International Law Commission work. With a careful enquiry into the debates of the International Law Commission he lays bare some of the shortcomings of the International Law Commission’s approach to the topic. The main point of his analysis is whether international organisations play a role in their own name and not as agents of States in the production of rules of customary international law. He articulates a principled approach to the relation between international organisations and custom based on the notion of autonomy. He argues that autonomy constitutes an inherent element of international legal personality. On this basis, he argues that international law confers lawmaking power on both States and international organisations. By critically approaching the work of the International Law Commission, Voulgaris engages in a broader reflection on the lawmaking capacity of international organisations.

The volume continues with two contributions addressing opinio juris. Brölmann looks at the role of the juridical will of legal actors, and international organisations in particular, in the formation of customary international law. She addresses two main aspects, the volonté distincte and intentional state. Brölmann’s point is that the difficulties in defining the juridical will of international organisations likely result from the mechanistic, functionalist view of international organisations. She concludes that while the modest role of international organisations as independent lawmakers in the Conclusions may be justified, ultimately it will be untenable in the light of international organisations’ full-fledged participation in international law. In turn, Droubi looks into whether international organisations, which knowingly have many instruments to shape the behaviour of States, are also capable of shaping the opinio juris of States. For instance, would an international organisation such as the United Nations be able to promote, or at least influence, the formation of opinio juris that is consistent with findings and recommendations of the Intergovernmental Panel on Climate Change? He argues that, although international organisations have a wide array of instruments to affect and even shape the collective behaviour of States, they face almost unsurmountable challenges when it comes to shaping the opinio juris of States in a desired form – including pursuant to scientific standards. He develops the argument by revisiting the concept of opinio juris, which leads him to define opinio juris as an institutional object. This permits the unveiling of the various manners in which international organisations might interfere in the process of formation of opinio juris. He then turns to the ability of international organisations to promote opinio juris with a desired content. Droubi concludes by playing down the possibility that international organisations are able to coordinate international processes in a manner to shape opinio juris pursuant to desired standards.

Gasbarri puts forward a theoretical framework for the role of international organisations in the formation of customary international law that aims at reconciling their traditional, conflicting conceptualisations as either agents of States or autonomous actors. Through the discussion of three case studies concerning what he identifies as ‘anomalies’ in the development of so-called ‘objective regimes’, he articulates a theoretical framework on the role of international organisations in the formation of customary international law that acknowledges their dual nature.

Meguro seeks to clarify the role of non-State actors in custom-making processes by shouldering aside the dominant two-element understanding of opinio juris and practice. She demonstrates that the mainstream approaches are incognisant to the role of non-State actors because of constructions that are highly questionable. Maiko unveils the shortcomings of the prevalent approach to opinio juris by emphasising its reliance on an anthropomorphic concept of opinio juris. Turning to practice, she emphasises the role of domestic non-State actors in the creation of international norms that shape State practice. She concludes with some remarks about the general implications of her approach to the doctrine of customary law as a whole.

Cardenas argues that non-State actors play an important role in the formation of customary international law. After recalling that the two-element approach to customary international law is just one possible perspective to the study of the topic, Cardenas opts for a social perspective of customary international law, which allows him to argue that the community of international lawyers can possibly give weight to non-State actors’ positions in the formation of customary international law. Indeed, he approaches international law as socially constructed argumentative practice to claim that customary international law is the product of successful argumentative campaigns undertaken by international lawyers. While the latter often work for States, they may also represent the interests of non-State actors. On this ground, he posits that, in ascertaining customary international law, although the views of State lawyers tend to be prioritised, those of lawyers working for non-State actors are often taken into due consideration.

D’Aspremont returns to the last decade of scholarly reflections on the question of non-State actors and customary international law and revisits some of the specific argumentative constructions and presuppositions that have informed – and continue to inform – discourses on the contribution of non-State actors and international law. His chapter is specifically premised on the idea that international legal thought and practice on non-State actors and customary international law have remained chained by certain modes of reasoning and category of thoughts which have been precluding any renewal of scholarly reflection on the matter. It is submitted in this chapter that, in order to make a chance of novelty and creative thinking, any new wave of scholarly reflections on the contribution of non-State actors to custom-forming processes – including this very volume – must reinvent the very categories around which international legal discourses are currently articulated.

The second part of the volume begins with Sir Michael Wood’s chapter. With an emphasis on the role of international organisations and non-State actors to the formation of customary international law, this chapter recalls some of the key choices made by the International Law Commission in its work on the identification of customary international law. In doing so, this chapter offers some reactions to a number of criticisms made by international legal scholars, including some of the contributors to this volume.

Bílková critically engages the view on non-State actors that the Conclusions adopt. She gives an impressive account of the history of the drafting process that led to the adoption of the Conclusions – which in itself is a valuable source of information for any student of the topic. Then, Bílková challenges the International Law Commission approach to the role of non-State actors in the process of emergence of customary international law, and puts forward a strong case in that the International Law Commission fails to do justice to the plurality of roles that non-State actors currently play in the formation and identification of customary international law.

Pereira addresses a specific aspect of International Law Commission work that resulted in the Conclusions, namely, the manner in which the International Law Commission defines its own output vis-à-vis the formation of customary international law. While the International Law Commission specifically addresses ‘teachings of publicists’ and judgments, it has chosen to simply mention the relevance of its own work – which it did in the commentary opening Part V. Pereira argues that the Commission was right in not including its work under the ‘teachings of publicists’ heading.

Deplano examines the role of resolutions adopted by intergovernmental organisations in the Conclusions. Through a careful empirical study, Deplano shows that over time resolutions of the General Assembly have acquired a systemic character. Therefore, she claims that these resolutions do not exist in isolation from each other. In developing her argument, Deplano shows that a rule of customary international law, which resolutions may generate, lays outside the text of the resolutions. Rather, the resolutions trigger the rule in question. On these grounds, she argues that, insofar as the purpose of the International Law Commission is to provide a methodology for identifying a customary rule, then the Commission has set out an impossible task for itself in what respects the role of resolutions in the formation of customary international law.

Merlin’s chapter, which looks at the role of the United Nations in the formation and identification of customary international law, argues that it can be described as a ‘specificity within a specificity’. He emphasises that the contribution of the United Nations to the formation and identification of rules of customary international law is not uniform; rather, it varies from organ to organ. In his chapter, Merlin is mostly concerned with the Secretariat and Secretary-General. He argues that the universal character of the United Nations places it in a better position relative to other international organisations to contribute, at various levels, in various ways and often involving the combined conduct of several organs, to the formation and expression of general rules of customary international law. Looking at the Secretariat, Merlin recalls that it interacts, e.g. with the Security Council and the General Assembly as well as the International Law Commission, which typically is vested with the double mandate of promoting the development of international law and its codification.

Veber seeks to demonstrate an increasingly important role of international organisations in relation to the formation of customary international law rules by virtue of the sanctions they adopt in response to violations of erga omnes obligations. She argues that through the adoption of sanctions to uphold rules of international law, international organisations can contribute to these rules acquiring the status of customary international law. However, she posits that the contribution of sanctions to the formation of custom varies significantly on a case-by-case basis. Contrasting cases in which the underlying rules have erga omnes character with cases in which they do not have, Veber concludes that the potential for customary lawmaking is greater when the erga omnes status of the underlying rule is not confirmed yet.

Müller looks at the ten-year effort that the International Committee of the Red Cross carried out to complete its study on customary international humanitarian law, which was published in 2005. The study identified 161 rules of customary international humanitarian law and presented the material collected in their determination. Müller explains that the International Committee of the Red Cross needed to consider many of the methodological questions that the International Law Commission faces today in its work on the identification of customary international law. Like the International Law Commission’s draft conclusions on that topic adopted at first reading in 2016, the study is based on the fundamental requirement of two elements: a general practice that is accepted as law (opinio juris). Among the issues arising from this approach that the study, like the International Law Commission, had to address were the questions whose practice it is that forms rules of customary international law and whether actors other than States could be relevant in this context.

McCall-Smith looks at human rights treaty bodies to argue that the responses by States to human rights treaty body interpretations warrants the conclusion that treaty bodies can, and do, contribute to the development of customary international law, albeit in often subtle ways and through their relationships with States parties.

Worster addresses international territorial administrations. He argues that when an international organisation becomes entangled with a State government, the normal participation in the formation of customary international law becomes confused. He provides a survey of practice citing to the acts of international territorial administrations to show that it is possible for these governance arrangements to contribute to customary international law in the same manner as States, even though those acts are formally undertaken by by an international organisation.

Berkes argues that the activities of de facto regimes can be considered as properly speaking ‘practice’ that contributes to the formation, or expression, of rules of customary international law under two scenarios. Firstly, the custom-creating or custom-strengthening conduct of the de facto regime can be attributed to a State, usually to an occupying power or a State supporting in various means the de facto regime by exercising effective control or at least decisive influence over it. Berkes explains that in this first scenario the conduct of de facto regimes can be regarded as ‘practice’ for the identification of customary international law. He also argues that, lege ferenda, even without attributing the conduct of a de facto regime to a State, its conduct should be taken into account as strengthening the practice forming customary international law at least in subject matters governing the rights and obligations of the de facto regime itself. Although both scenarios may raise various theoretical and practical objections, Berkes explains that in areas under-regulated by international law, the conduct of de facto regimes may be relevant as ‘practice’ revealing a State’s (usually the territorial or an outside State’s) practice.

Yamashita argues that investors have emerged as the most powerful claimants who certainly influence the clarification of customary international law rules through investor–State dispute settlement on the international sphere. Her objective is to answer the question of how and to what extent references to customary international law in investor–State dispute settlement may influence the formation of customary international law. She proposes to answer these questions through the combination of two concepts – namely, ‘framing’ and ‘spilling-over effect’. Investors who raise questions of customary international law have a significant ability to frame the debates that lead to a final award. These arguments have a spill-over effect, i.e. their impact can be felt beyond the immediate realities of the case at hand. Through a well-developed case study, she ascertains the impact of these arguments.

In her chapter, Azarova offers a constructivist account of the proliferating roles of non-governmental organisations in the making of customary international law. While these roles are largely informal, and non-governmental organisations’ influence on the content and interpretation of customary international law norms is primarily indirect, non-governmental organisations contribute to the formation of customary international law through an increasingly diverse set of activities, which has been particularly influential when implemented in a strategic and concerted manner. Non-governmental organisations’ documentation, litigation, lobbying, and other forms of advocacy have contributed to treaty-making and ratification; to the domestication and internalisation of international norms and processes, including domestic accountability and remedies; and to codifying the obligations of, and stimulating practice by, non-State actors such as business and armed groups. Despite a broad acknowledgement of the increasing involvement of non-governmental organisations in global governance by scholars and practitioners, their role in customary international lawmaking remains under-appreciated. To understand the increased influence of non-governmental organisations on the identification, formation, and application of customary international law rules, the chapter offers a differentiated, effects-based account of non-governmental organisations’ participation in customary international lawmaking.

On a final note, this volume results from a 2017 conference hosted by the Manchester International Law Centre, University of Manchester, with the support of the University of Manchester, the Interest Group on International Organizations of the European Society of International Law, and of the São Paulo Research Foundation, and which counted with academics and practitioners from different parts of the world and with the kind participation of Sir Michael Wood. May all those who made this volume and the preceding conference possible be thanked. Their efforts and generosity allow international lawyers’ story-telling about customary international law to continue.

1 Institut de Droit International, ‘The Elaboration of General Multilateral Conventions and of Non-Contractual Instruments Having a Normative Function or Objective’ (1987) Session of Cairo, notably Conclusion 22 (‘[a]‌ Resolution may contribute to the consolidation of State practice, or to the formation of the opinio juris communis ’); International Committee of the Red Cross, ‘Study on Customary International Humanitarian Law’ (2007) 2007 30IC/07/8.3 xxxviii (‘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 necessitates )’); United Nations General Assembly Resolution 203 (73rd Sess) (11 January 2019) ‘Identification of customary international law’ A/RES/73/203 and Annex ‘Identification of customary international law’, Conclusion 2 (‘[t]o determine the existence and content of a rule of customary international law, it is necessary to ascertain whether there is a general practice that is accepted as law ( opinio juris )’). Even the nuanced approach that the International Law Association adopts speaks of the two elements: see International Law Association, ‘Final Report of the Committee on Formation of Customary (General) International Law: Statement of Principles Applicable to the Formation of General Customary International Law’, Principle 16 Commentary (c) (‘It may well be true (though trivial) to observe that States will usually or always hold an opinio juris about an established rule of law … where it can be shown that an opinio juris exists about a practice, that will be sufficient’).

2 See Institut de Droit International (n 1) Conclusion 6 (a) (‘intent and expectation of States’) (d) (‘extent of support for the Resolution’); Conclusion 8 (‘it is desirable that States particularly interested in the matter be enabled to take part in the deliberations of the organ and in the elaboration of the draft’); Conclusion 14 (‘In situations where a rule of customary law is emerging from State practice or where there is still doubt whether a rule, though already applied by an international organ or by some States, is a rule of law, a Resolution adopted without negative vote or abstention may consolidate a custom or remove doubts that might have existed’). International Law Association 2000 (n 1) Principle 11 Commentary (b) (‘Organs of international organizations, and notably the United Nations General Assembly, also from time to time adopt resolutions containing statements about customary international law. Formally, since the decision is recorded as a resolution of (the organ of the) organization, its adoption is a piece of practice by the organization; and some writers treat it in this way. However, in the context of the formation of customary international law, it is probably best regarded as a series of verbal acts by the individual member States participating in that organ. If so, it would add little or nothing to the weight of such practice by the member States themselves to treat the resolution itself (as distinct from voting for it) as a further piece of practice, this time on the part of the organization’); also Principles 31 and 32 and their Commentary (resolutions of the United Nations General Assembly). cf with International Law Commission, ‘Identification of Customary International Law, Text of the Draft Conclusions and commentaries thereto’ [2018] Report of the International Law Commission Seventieth session (30 April–1 June and 2 July–10 August 2018) International Law Commission Report, A/73/10, 2018, chap V, para 66, Conclusion 4 Commentary (7) (‘As a general rule, the more directly a practice of an international organization is carried out on behalf of its member States or endorsed by them, and the larger the number of such member States, the greater weight it may have in relation to the formation, or expression, of rules of customary international law’).

3 See , for all, International Law Commission 2018 (n 2) Conclusion 4 Commentary para 4–6 (suggesting the opnio juris of international organisations are relevant in respect to matters upon which States have accorded them either exclusive competence or specific powers). For insightful accounts of this point, see Chapters 2 and 3 in this volume.

4 International Law Association 2000 (n 1) Principle 7 Commentary; Draft Conclusion with Commentary (n 2) Conclusion 4.3 and Commentary (9) and (10).

5 See International Law Association 2000 (n 1) Principle 7 (‘Acts of individuals, corporations etc. do not count as State practice, unless carried out on behalf of the State or adopted (ratified) by it’); Resolution A/RES/73/2–3 (n 1) Conclusion 4(3) (‘Conduct of other actors is not practice that contributes to the formation, or expression, of rules of customary international law, but may be relevant when assessing the practice referred to in paragraphs 1 and 2’).

6 As the bibliography that he had amassed and submitted as part of his last reports confirms. cf ‘Fourth report on identification of customary international law by Michael Wood, Special Rapporteur. Addendum. Annex II. Identification of customary international law: bibliography’ (2016) International Law Commission Sixty-eighth session, UN Doc A/CN.4/695/Add.1 (25 May 2016); and ‘Fifth report on identification of customary international law by Michael Wood, Special Rapporteur. Addendum. Annex II. Identification of customary international law: revised bibliography’ (2018) International Law Commission Seventieth session, UN Doc A/CN.4/717/Add.1 (6 June 2018).

7 International Law Commission (n 2), General Commentary 2.

8 ibid.

9 Note the unfolding of the story throughout the reports submitted by Sir Michael Wood to the International Law Commission and the records of the debates held by the International Law Commission in ‘Analytical Guide to the Work of the International Law Commission: Identification of Customary International Law’ http://legal.un.org/ilc/guide/1_13.shtml accessed 23 February 2019.

10 General Assembly Resolution 203 (n 1), operative paras 1 and 4.

11 International Law Commission 2018 (n 2), para 63.

12 General Assembly Resolution 203 (n 1), operative para 5.

13 See e.g. International Law Commission, ‘Sixty-Fourth Session (Second Part) Provisional Summary Record of the 3150th Meeting’ [2012] UN Doc n A/CN.4/SR.3150, 11 (statement by Mr Forteau, who ‘did not see how the formation of custom fell within the Commission’s mandate and thought the focus should be on the much more practical matter of identifying customary international law, meaning the specific evidence of custom’); and International Law Commission, ‘Sixty-Fourth Session (Second Part) Provisional Summary Record of the 3151st Meeting’ [2013] UN Doc n A/CN 4/SR 3151, 13 (statement by Mr Nolte, who ‘did not … subscribe to the idea that a clarification of the formation of customary international law would be less important and would be merely an academic exercise. States and practitioners … also wanted to know how to explain to their national courts and other bodies why and under which circumstances those means led to the conclusion that a particular rule was or was not a rule of customary international law. Of course, in trying to explain the formation of customary international law, the Commission ran the risk of becoming involved in a discussion of certain general questions of principle, but that was inevitable in the current exercise. If the Commission did not deal with such issues, it would not meet the expectations of States and the international community at large, and the result of its work might be called into question too easily’).

14 International Law Commission, ‘Identification of Customary International Law’ [2014] Report of the International Law Commission Sixty-sixth session (5 May–6 June and 7 July–8 August 2014) 74, para 172.

15 On formation, see , above, n 13. On the weight of international organisations, see International Law Commission 2014 (n 14), 74 para 159 (‘Some members of the Commission were of the view that the use of the word primarily was misguided as it suggested that the practice of entities other than the State could be relevant. Those members were of the view that the practice of international organizations was not to be taken into account in the process of identification of rules of customary international law. Other members considered that the practice of international organizations was only pertinent to the extent it reflected the practice of States. Some other members, however, agreed with the Special Rapporteur that the practice of international organizations as such could be relevant to the establishment of customary rules, particularly in regards to certain fields of activity within the mandates of those organizations’). See International Law Commission, ‘Identification of Customary International Law’ [2015] Report of the International Law Commission Sixty-seventh session (4 May–5 June and 6 July–7 August 2015) 38 paras 83–4 and 89. On non-State actors, see ibid para 90 (‘The draft conclusion proposed by the Special Rapporteur that the conduct of other non-State actors was not practice for the purposes of the formation or identification was supported by several members of the Commission … Some members of the Commission considered the proposal to be too strict, in particular in the light of the importance of the practice of certain non-State actors, such as the International Committee of the Red Cross, as well as in view of the importance of activities involving both States and non-State actors’).

16 This is not to say that the International Law Commission, and Sir Michael in particular, have not been aware of these debates. In fact, Sir Michael and the International Law Commission have engaged in an extensive dialogue with different actors, including academics. E.g. Stephen Mathias, ‘Editorial Comment: The Work of the International Law Commission on Identification of Customary International Law: A View from the Perspective of the Office of Legal Affairs’ (2016) Chinese Journal of International Law 17; Sienho Yee, ‘Report on the International Law Commission Project on Identification of Customary International Law’ (2015) Chinese Journal of International Law 375. See also Niels Blokker, ‘International Organizations and Customary International Law’ (2017) 14 International Organizations Law Review 1; George Rodrigo Bandeira Galindo and César Yip, ‘Customary International Law and the Third World: Do Not Step on