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.