Sufyan Droubi is Reader in Public International Law at the University of DundeeJean d’Aspremont is Professor of International Law at Sciences Po Paris and the University of Manchester

‘Where the ILC stopped in its 2018 Conclusions on Identification of Customary International Law, this book continues. It offers a rich variety of theoretical and practice-inspired reflections, doing justice to the ways in which international organizations and non-state actors contribute to the development of customary international law.’—Niels Blokker, Professor emeritus of International Institutional Law (Schermers Chair), Leiden University'Overall, the book is a great source for anyone interested in the general theoretical issues of customary international law, as well as those who have an interest in narrower questions on the role that international organisations and non-state actors have at different stages of the making of customary international law.' —Journal of International Law of Peace and Armed Conflict'The book is a great source for anyone interested in the general theoretical issues of customary international law, as well as those who have an interest in narrower questions on the role that international organisations and non-state actors have at different stages of the making of customary international law. Outside of theory, the volume offers the reader an opportunity to look at the theoretical issues from a practical perspective.' —Humanitäres Völkerrecht

• Introduction: Stories about International Organisations, Non-State Actors and the Formation of Customary International Law – Sufyan Droubi and Jean d’Aspremont1 International Organisations as Autonomous Actors – Nikolaos Voulgaris2 Capturing the Juridical Will – Catherine Brölmann 3 Opinio Juris: Between Mental States and Institutional Objects – Sufyan Droubi4 Beyond the Either-Or Paradigm – Lorenzo Gasbarri5 Between Anthropomorphism and Artificial Unity – Maiko Meguro6 Custom as the product of successful argumentative campaigns – Fabian Cardenas7 Unlearning some common tropes – Jean d’Aspremont8 International Organizations and non-State actors in the International Law Commission’s Conclusions on Identification of Customary International law – Michael Wood9 The International Law Commission Perspective on Non-State Actors and Customary International Law – Veronika Bílková10 The International Law Commission in the Eyes of the International Law Commission: Mirror or Looking-glass? – Luíza Leão Soares Pereira11 The Riddle of Custom: General Assembly Resolutions – Rossana Deplano12 The United Nations Secretariat and Custom – Jean-Baptiste Merlin13 The Making of Custom through Sanctions of International Organisations – Maruša T. Veber14 The International Committee of the Red Cross and Custom – Iris Müller15 Treaty Bodies and States: Shaping Custom – Kasey McCall-Smith16 The Contribution to Customary International Law by Territories under International Administration – William Thomas Worster17 The formation of customary international law by de facto regimes – Antal Berkes18 Investors in the Formation of Customary International Law – Tomoko Yamashita19 Adjudicators, Guardians, and Enforcers: Taking the Role of Non-Governmental Organisations in Customary International Law-Making Seriously – Valentina AzarovaIndex

Sufyan Droubi is Reader in Public International Law at the University of DundeeJean d’Aspremont is Professor of International Law at Sciences Po Paris and the University of Manchester

‘Where the ILC stopped in its 2018 Conclusions on Identification of Customary International Law, this book continues. It offers a rich variety of theoretical and practice-inspired reflections, doing justice to the ways in which international organizations and non-state actors contribute to the development of customary international law.’—Niels Blokker, Professor emeritus of International Institutional Law (Schermers Chair), Leiden University'Overall, the book is a great source for anyone interested in the general theoretical issues of customary international law, as well as those who have an interest in narrower questions on the role that international organisations and non-state actors have at different stages of the making of customary international law.' —Journal of International Law of Peace and Armed Conflict'The book is a great source for anyone interested in the general theoretical issues of customary international law, as well as those who have an interest in narrower questions on the role that international organisations and non-state actors have at different stages of the making of customary international law. Outside of theory, the volume offers the reader an opportunity to look at the theoretical issues from a practical perspective.' —Humanitäres Völkerrecht

• Introduction: Stories about International Organisations, Non-State Actors and the Formation of Customary International Law – Sufyan Droubi and Jean d’Aspremont1 International Organisations as Autonomous Actors – Nikolaos Voulgaris2 Capturing the Juridical Will – Catherine Brölmann 3 Opinio Juris: Between Mental States and Institutional Objects – Sufyan Droubi4 Beyond the Either-Or Paradigm – Lorenzo Gasbarri5 Between Anthropomorphism and Artificial Unity – Maiko Meguro6 Custom as the product of successful argumentative campaigns – Fabian Cardenas7 Unlearning some common tropes – Jean d’Aspremont8 International Organizations and non-State actors in the International Law Commission’s Conclusions on Identification of Customary International law – Michael Wood9 The International Law Commission Perspective on Non-State Actors and Customary International Law – Veronika Bílková10 The International Law Commission in the Eyes of the International Law Commission: Mirror or Looking-glass? – Luíza Leão Soares Pereira11 The Riddle of Custom: General Assembly Resolutions – Rossana Deplano12 The United Nations Secretariat and Custom – Jean-Baptiste Merlin13 The Making of Custom through Sanctions of International Organisations – Maruša T. Veber14 The International Committee of the Red Cross and Custom – Iris Müller15 Treaty Bodies and States: Shaping Custom – Kasey McCall-Smith16 The Contribution to Customary International Law by Territories under International Administration – William Thomas Worster17 The formation of customary international law by de facto regimes – Antal Berkes18 Investors in the Formation of Customary International Law – Tomoko Yamashita19 Adjudicators, Guardians, and Enforcers: Taking the Role of Non-Governmental Organisations in Customary International Law-Making Seriously – Valentina AzarovaIndex

Sufyan Droubi is Reader in Public International Law at the University of DundeeJean d’Aspremont is Professor of International Law at Sciences Po Paris and the University of Manchester

‘Where the ILC stopped in its 2018 Conclusions on Identification of Customary International Law, this book continues. It offers a rich variety of theoretical and practice-inspired reflections, doing justice to the ways in which international organizations and non-state actors contribute to the development of customary international law.’—Niels Blokker, Professor emeritus of International Institutional Law (Schermers Chair), Leiden University'Overall, the book is a great source for anyone interested in the general theoretical issues of customary international law, as well as those who have an interest in narrower questions on the role that international organisations and non-state actors have at different stages of the making of customary international law.' —Journal of International Law of Peace and Armed Conflict'The book is a great source for anyone interested in the general theoretical issues of customary international law, as well as those who have an interest in narrower questions on the role that international organisations and non-state actors have at different stages of the making of customary international law. Outside of theory, the volume offers the reader an opportunity to look at the theoretical issues from a practical perspective.' —Humanitäres Völkerrecht

• Introduction: Stories about International Organisations, Non-State Actors and the Formation of Customary International Law – Sufyan Droubi and Jean d’Aspremont1 International Organisations as Autonomous Actors – Nikolaos Voulgaris2 Capturing the Juridical Will – Catherine Brölmann 3 Opinio Juris: Between Mental States and Institutional Objects – Sufyan Droubi4 Beyond the Either-Or Paradigm – Lorenzo Gasbarri5 Between Anthropomorphism and Artificial Unity – Maiko Meguro6 Custom as the product of successful argumentative campaigns – Fabian Cardenas7 Unlearning some common tropes – Jean d’Aspremont8 International Organizations and non-State actors in the International Law Commission’s Conclusions on Identification of Customary International law – Michael Wood9 The International Law Commission Perspective on Non-State Actors and Customary International Law – Veronika Bílková10 The International Law Commission in the Eyes of the International Law Commission: Mirror or Looking-glass? – Luíza Leão Soares Pereira11 The Riddle of Custom: General Assembly Resolutions – Rossana Deplano12 The United Nations Secretariat and Custom – Jean-Baptiste Merlin13 The Making of Custom through Sanctions of International Organisations – Maruša T. Veber14 The International Committee of the Red Cross and Custom – Iris Müller15 Treaty Bodies and States: Shaping Custom – Kasey McCall-Smith16 The Contribution to Customary International Law by Territories under International Administration – William Thomas Worster17 The formation of customary international law by de facto regimes – Antal Berkes18 Investors in the Formation of Customary International Law – Tomoko Yamashita19 Adjudicators, Guardians, and Enforcers: Taking the Role of Non-Governmental Organisations in Customary International Law-Making Seriously – Valentina AzarovaIndex