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.

• 1. Shifting landscape of interpretation in international law: sources, actors, subject-matters Sotirios Ioannis Lekkas, Nina Mileva and Panos Merkouris; Part I. Unity, Diversity, and Evolution of Interpretation Across Sources of International Law: 2. Systemic integrational and public law elements in the sources of international law Jure Vidmar; 3. Comparative reasoning in international investment law and arbitration Yannick Radi; 4. Interpretation of customary international environmental law before international courts Ilias Plakokefalos; Part II. Unity, Diversity, and Evolution of Interpretation of International Law across Actors: 5. Interpretation of customary international law in an institutional context Catherine Brölmann; 6. Treaty interpretation in the fog of war: the evolution of the ICRC's methodology Ellen Polcinski; 7. Treaty interpretation practices of human rights bodies: thrown for a loop or thrown int the crucible Marlies Hesselmann; 8. Mutually supportive interpretation of the law of the sea, international biodiversity law, and human rights – clarifying the path towards transformative change Elisa Morgera; Part III. Unity, Diversity, and Evolution of Interpretation across Subject-Matters of International Law: 9. Application of the general rule of interpretation by the WTO dispute settlement system Gabrielle Marceau, Maria George and Vishakha Raj; 10. Methods of interpretation of international investment law: the use of the object and purpose of investment treaties in interpreting territoriality Thomas Nektarios Papanastasiou; 11. Core international crimes at the interface: in search of unity amidst diversity in the interpretation of international criminal law Olympia Bekou; 12. Crimes against humanity and customary international law Leila Sadat; Concluding Observations: 13. The practice of interpretation in international law: unity, diversity, and evolution Judge Ineta Ziemele.

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.

• 1. Shifting landscape of interpretation in international law: sources, actors, subject-matters Sotirios Ioannis Lekkas, Nina Mileva and Panos Merkouris; Part I. Unity, Diversity, and Evolution of Interpretation Across Sources of International Law: 2. Systemic integrational and public law elements in the sources of international law Jure Vidmar; 3. Comparative reasoning in international investment law and arbitration Yannick Radi; 4. Interpretation of customary international environmental law before international courts Ilias Plakokefalos; Part II. Unity, Diversity, and Evolution of Interpretation of International Law across Actors: 5. Interpretation of customary international law in an institutional context Catherine Brölmann; 6. Treaty interpretation in the fog of war: the evolution of the ICRC's methodology Ellen Polcinski; 7. Treaty interpretation practices of human rights bodies: thrown for a loop or thrown int the crucible Marlies Hesselmann; 8. Mutually supportive interpretation of the law of the sea, international biodiversity law, and human rights – clarifying the path towards transformative change Elisa Morgera; Part III. Unity, Diversity, and Evolution of Interpretation across Subject-Matters of International Law: 9. Application of the general rule of interpretation by the WTO dispute settlement system Gabrielle Marceau, Maria George and Vishakha Raj; 10. Methods of interpretation of international investment law: the use of the object and purpose of investment treaties in interpreting territoriality Thomas Nektarios Papanastasiou; 11. Core international crimes at the interface: in search of unity amidst diversity in the interpretation of international criminal law Olympia Bekou; 12. Crimes against humanity and customary international law Leila Sadat; Concluding Observations: 13. The practice of interpretation in international law: unity, diversity, and evolution Judge Ineta Ziemele.