The Practice of Interpretation in International Law: Unity, Diversity, and Evolution (The Rules of Interpretation of Customary International Law) - Hardcover

Hardcover

ISBN 10: 1009599089 ISBN 13: 9781009599085

Publisher: Cambridge University Press, 2026

Synopsis

Does a unified law of interpretation exist? Can it be applied to all legal rules, regardless of their source, interpreter, or subject matter? This volume offers a comprehensive exploration of how interpretation is practiced across the diverse landscape of international law. Drawing on contributions from leading scholars and practitioners, the book examines interpretation through the lenses of multiple actors, sources, and regimes, revealing three core themes. Unity emerges in shared interpretative methods, rooted in the Vienna Convention on the Law of Treaties and its customary counterparts. Diversity appears in the distinctive approaches found within specialised legal regimes. Evolution is seen in the growing range of materials considered during interpretation. Rich in comparative insights, this volume will be an essential reference for researchers, practitioners, and anyone interested in the dynamic processes that shape meaning in international law. This title is also available as open access on Cambridge Core.

About this title

About the Authors

Sotirios Ioannis Lekkas is Lecturer in International Law at the University of Sheffield. He was postdoctoral researcher for the ERC-funded TRICI-Law project at the University of Groningen. His DPhil thesis at the University of Oxford, 'Duality of Responsibility in International Law,' won the 2019–21 Hellenic Society of International Law Georges Tenekides Prize.

Nina Mileva is Assistant Professor of International Law at the University of Groningen. She completed her Ph.D. (University of Groningen) in 2023 within the ERC-funded project TRICI-Law. Dr. Mileva is a member of the Coordinating Committee of the Interest Group on International Legal Theory and Philosophy (IGILTP) of the European Society of International Law (ESIL).

Panos Merkouris is Professor of International Law at the University of Groningen. His five-year project on The Rules of Interpretation of Customary International Law was awarded an ERC Starting Grant (ERC grant agreement no 759728). Professor Merkouris is a member of the editorial boards of the Netherlands Yearbook of International Law (NYIL) and the International Community Law Review (ICLR). He was also the co-rapporteur of the ILA Study Group on the Content and Evolution of Rules of Interpretation in International Law.

Ivo Tarik de Vries Zou has written a doctoral thesis on the use of soft law in treaty interpretation and the determination of customary rules at the University of Groningen. He has also published on issues of international dispute settlement and worked both as an academic as well as for practitioners.

Edition details

• Publisher: Cambridge University Press
• Publication date: 2026
• Language: English
• ISBN 10: 1009599089
• ISBN 13: 9781009599085
• Binding: Hardcover
• Number of pages: 435
• Editor: Edited By Sotirios Ioannis Lekkas