Marina Fortuna is an Assistant Professor at the University of Groningen and member of the TRICI-law project team. Her research focuses primarily on the practice of international courts, which she examines from the perspective of different topics from general international law. Kostia Gorobets is Assistant Professor of International Law at the University of Groningen. He specialises in analytical jurisprudence and philosophy of international law, as well as in their interplay. Panos Merkouris is Professor of International Law at the University of Groningen. He is the Principal Investigator of the TRICI-Law project (ERC Grant Agreement No. 759728). Professor Merkouris has written extensively on law of treaties, sources and interpretation, most recently authoring Interpretation of Customary International Law: of Methods and Limits (2023). Andreas Føllesdal is Professor of Political Philosophy at the Faculty of Law, University of Oslo. He is the co-director of PluriCourts and was the Principal Investigator of ERC Advanced Grant MultiRights 2011–16. He publishes in the field of political philosophy, mainly on international political and legal theory, globalisation/Europeanisation and human rights. Geir Ulfstein is Professor emeritus of International Law at the University of Oslo and Co-Director of PluriCourts. He is also the President of the Norwegian Branch of the International Law Association (ILA) and winner of the University of Oslo Research Award 2021 (with Andreas Føllesdal). He has published in different areas of international law, including the law of the sea, international environmental law, international human rights, international institutional law and international courts. Pauline Westerman is Professor in the Philosophy of Law at the University of Groningen, member of staff at the Academy for Legislation in the Hague and a member of the Royal Dutch Academy of Sciences. Her research focuses on the making of law, the formation of soft law and the emergence and development of international law.

• Part I. Theoretical Approaches to CIL and its Interpretation: 1. The illusion of Gold-Digging: interpretation of State practice Pauline Westerman; 2. Addressing the chronological Paradox: Constitutive rules and the constructive interpretation of CIL Henrique Marcos; 3. Interpreting the plural sources of CIL Harlan Grant Cohen; 4. Interpretation dynamics in CIL: an entropic approach Eleni Micha; Part II. Methods of CIL Interpretation in International Courts; Tools of the Trade: 5. The application of logic and reason in CIL interpretation William Worster; 6. The interpretation of 'direction and control' in the investor State Arbitration: the case of State-owned enterprises Paula Baldini Miranda Da Cruz; 7. The court of justice of the EU and CIL interpretation: close encounters of a third kind? Tamás Molnár; 8. Judicial effectiveness or judicial Ambiguity: is CIL an instrument for judicial activism in excess? Leoni Ayoub; 9. Judicial dialogue between International Courts in the interpretation of customary International Human Rights Law Silviana Cocan; Part III. CIL and its Interpretation in the Normative Universe: drifting towards Coherence?: 10. 'General principles of law' and the interpretation of CIL Craig Eggett; 11. The role of treaties and general principles of law in the interpretation of customary rules Marina Fortuna; 12. Reconciling conflicting norms of CIL – towards a mode of practical concordance at the ICJ Raphael Oidtmann; 13. Indicators of coherence and interpretation of CIL Charalampos Giannakopoulos; Bibliography, Index.

Marina Fortuna is an Assistant Professor at the University of Groningen and member of the TRICI-law project team. Her research focuses primarily on the practice of international courts, which she examines from the perspective of different topics from general international law. Kostia Gorobets is Assistant Professor of International Law at the University of Groningen. He specialises in analytical jurisprudence and philosophy of international law, as well as in their interplay. Panos Merkouris is Professor of International Law at the University of Groningen. He is the Principal Investigator of the TRICI-Law project (ERC Grant Agreement No. 759728). Professor Merkouris has written extensively on law of treaties, sources and interpretation, most recently authoring Interpretation of Customary International Law: of Methods and Limits (2023). Andreas Føllesdal is Professor of Political Philosophy at the Faculty of Law, University of Oslo. He is the co-director of PluriCourts and was the Principal Investigator of ERC Advanced Grant MultiRights 2011–16. He publishes in the field of political philosophy, mainly on international political and legal theory, globalisation/Europeanisation and human rights. Geir Ulfstein is Professor emeritus of International Law at the University of Oslo and Co-Director of PluriCourts. He is also the President of the Norwegian Branch of the International Law Association (ILA) and winner of the University of Oslo Research Award 2021 (with Andreas Føllesdal). He has published in different areas of international law, including the law of the sea, international environmental law, international human rights, international institutional law and international courts. Pauline Westerman is Professor in the Philosophy of Law at the University of Groningen, member of staff at the Academy for Legislation in the Hague and a member of the Royal Dutch Academy of Sciences. Her research focuses on the making of law, the formation of soft law and the emergence and development of international law.

• Part I. Theoretical Approaches to CIL and its Interpretation: 1. The illusion of Gold-Digging: interpretation of State practice Pauline Westerman; 2. Addressing the chronological Paradox: Constitutive rules and the constructive interpretation of CIL Henrique Marcos; 3. Interpreting the plural sources of CIL Harlan Grant Cohen; 4. Interpretation dynamics in CIL: an entropic approach Eleni Micha; Part II. Methods of CIL Interpretation in International Courts; Tools of the Trade: 5. The application of logic and reason in CIL interpretation William Worster; 6. The interpretation of 'direction and control' in the investor State Arbitration: the case of State-owned enterprises Paula Baldini Miranda Da Cruz; 7. The court of justice of the EU and CIL interpretation: close encounters of a third kind? Tamás Molnár; 8. Judicial effectiveness or judicial Ambiguity: is CIL an instrument for judicial activism in excess? Leoni Ayoub; 9. Judicial dialogue between International Courts in the interpretation of customary International Human Rights Law Silviana Cocan; Part III. CIL and its Interpretation in the Normative Universe: drifting towards Coherence?: 10. 'General principles of law' and the interpretation of CIL Craig Eggett; 11. The role of treaties and general principles of law in the interpretation of customary rules Marina Fortuna; 12. Reconciling conflicting norms of CIL – towards a mode of practical concordance at the ICJ Raphael Oidtmann; 13. Indicators of coherence and interpretation of CIL Charalampos Giannakopoulos; Bibliography, Index.