This collection of essays provides the most comprehensive study of the theory and practice on the contribution of international organisations and non-state actors to the formation of customary international law. It offers new perspectives on one of the most complex questions about the making of international law, namely the possibility that actors other than states contributes to the making of customary international law. Making extensively reference to the case-law of international law courts and tribunals as well as the practice of treaty-monitoring bodies while also engaging with the most recent scholarly work on customary international law, this new volume provides innovative tools and guidance to legal scholars, researcher in law, law students, lecturers in law, practitioners, legal advisers, judges, arbitrators, and counsels as well as tools to address contemporary questions of international law-making.
