Several current international legal issues are related to the concept of legal personality, including the determination of international rights and duties of non-state actors and the legal capacities of transnational institutions. When addressing these issues, different understandings of legal personality are employed. These concepts consider different entities to be international persons, state different criteria for becoming one and attach different consequences to being one. Roland Portmann systematizes the different positions on international personality by spelling out the assumptions on which they rest and examining how they were substantiated in legal practice. He puts forward the argument that positions on international personality which strongly emphasize the role of states or effective actors rely on assumptions that have been discarded in present international law. The principal argument is that international law has to be conceived as an open system, wherein there is no presumption for or against certain entities enjoying international personality. "Legal Personality in International Law is a piece of interesting, solid, and well-reasoned legal scholarship." Leiden Journal of International Law "There is much to admire in this work that is in many respects [a] commendable piece of scholarship. The relative lack of literature on this topic means that Portmann’s book will no doubt find a place on the bookshelf of many international lawyers and particularly those interested in the historical and theoretical underpinnings of the main conceptions of international legal personality" Modern Law Review "The intellectual history that the book provides as well as the arguments that it advances constitute a remarkable contribution to the field. Legal Personality in International Law is on balance a terrific book, and it is likely to become a mandatory starting point for future works on the subjects of international law." British Yearbook of International Law This analysis of legal personality in international law combines theory and practical material. Roland Portmann is a Scientific Collaborator at the Swiss Ministry of Foreign Affairs, Directorate of International Law, Bern, and a Lecturer in Public International Law at the University of St Gallen, Switzerland.