Provides an in-depth study of the theory, history, practice, and interpretation of customary international law.

This book sets out to articulate a comprehensive theory of customary international law that can effectively resolve the conceptual and practical enigmas surrounding it. It takes a multidisciplinary approach and draws insights from international law, legal theory, political science, and game theory. It is anchored in a sophisticated ethical framework and explores the interrelationships between customary international law and ethics.

Although customary international law has long been an important source of rights and obligations in international relations, there has been extensive debate in recent years about whether this body of law is equipped to address complex modern problems such as climate change, international terrorism, and global financial instability. In addition, there is growing uncertainty about how, precisely, international and domestic courts should identify rules of customary international law. Custom's Future seeks to address this uncertainty by providing a better understanding of how customary international law has developed over time, the way in which it is applied in practice, and the challenges that it faces going forward. Reflecting an interdisciplinary mix of historical, empirical, economic, philosophical, and doctrinal analysis, and containing chapters by leading international law experts, it will be of use to lawyers, judges, and researchers alike.

This is the first book to explore the concept of 'Grotian Moments'. Named for Hugo Grotius, whose masterpiece De jure belli ac pacis helped marshal in the modern system of international law, Grotian Moments are transformative developments that generate the unique conditions for accelerated formation of customary international law. In periods of fundamental change, whether by technological advances, the commission of new forms of crimes against humanity, or the development of new means of warfare or terrorism, customary international law may form much more rapidly and with less state practice than is normally the case to keep up with the pace of developments. The book examines the historic underpinnings of the Grotian Moment concept, provides a theoretical framework for testing its existence and application, and analyzes six case studies of potential Grotian Moments: Nuremberg, the continental shelf, space law, the Yugoslavia Tribunal's Tadic decision, the 1999 NATO intervention in Serbia and the 9/11 terrorist attacks.

"The book guides the reader through an analysis of eight distinct performances at work in the discourse on customary international law. One of its key claims is that customary international law is not the surviving trace of an ancient law-making mechanism that used to be found in traditional societies. Indeed, as is shown throughout, customary international law is anything but ancient, and there is hardly any doctrine of international law that contains so many of the features of modern thinking. It is also argued that, contrary to mainstream opinion, customary international law is in fact shaped by texts, and originates from a textual environment"--Page 4 de la couverture.

This book provides a comprehensive account of the emergence of the customary law of human rights. It examines a range of human rights norms, and provides a useful guide to identifying those which can be described as customary.

Reexamining Customary International Law takes on the complex issues and controversies surrounding the history, theory, and practice of customary international law as it reexamines customary law's increasingly important role in world affairs. It incorporates the expertise of distinguished authors to probe many difficult issues that remain unresolved concerning the doctrine of customary law. At the same time, this book engages in a profound exploration of the practical role of customary international law in a variety of important fields, including humanitarian law, human rights law, and air and space law.

The contributors to this book describe, discuss, and evaluate the normative reframing brought about by the Treaty on the Prohibition of Nuclear Weapons (the Ban Treaty), taking you on a journey through its genesis and negotiation history to the shape of the emerging global nuclear order. Adopted by the United Nations on 7 July 2017, the Ban Treaty came into effect on 22 January 2021. For advocates and supporters, weapons that were always immoral are now also illegal. To critics, it represents a profound threat to the stability of the existing global nuclear order with the Nuclear Non-proliferation Treaty as the normative anchor. As the most significant leap in nuclear disarmament in fifty years and a rare case study of successful state-civil society partnership in multilateral diplomacy, the Ban Treaty challenges the established order. The book’s contributors are leading experts on the Ban Treaty, including senior scholars, policymakers and civil society activists. A vital guide to the Ban Treaty for students of nuclear disarmament, arms control and diplomacy as well as for policymakers in those fields.

Some legal rules are not laid down by a legislator but grow instead from informal social practices. In contract law, for example, the customs of merchants are used by courts to interpret the provisions of business contracts; in tort law, customs of best practice are used by courts to define professional responsibility. Nowhere are customary rules of law more prominent than in international law. The customs defining the obligations of each State to other States and, to some extent, to its own citizens, are often treated as legally binding. However, unlike natural law and positive law, customary law has received very little scholarly analysis. To remedy this neglect, a distinguished group of philosophers, historians and lawyers has been assembled to assess the nature and significance of customary law. The book offers fresh insights on this neglected and misunderstood form of law.

This book seeks to re-appreciate the concept of customary international law as a form of spontaneous societal self-organisation, and to develop the methodological consequences that ensue from this conception for the practice of its application. In pursuing this aim, the author draws from three different strands of scholarship that have not yet been considered in connection with one another: First, general jurisprudential theories of customary law; second, theories of customary international law, especially as they relate to international relations scholarship; and third, methodological approaches to the interpretation of international law. This expansive, philosophical layout of the book enables the author to put the conceptual enigmas of customary international law into a broader perspective. Among the issues discussed in the book are the dichotomy of its traditional and modern forms and the respective benefits and disadvantages of inductive and deductive approaches to its ascertainment. In the course of this analysis, the author draws insights from Friedrich August Hayek’s theory of law as a ‘spontaneous order’, an information-processing device which enables the participants of a legal system to make use of decentralised knowledge. The book argues that the major advantage of custom as a source of international law lies in the fact that it is the result of a gradual process of trial and error, rather than the product of deliberate planning. This makes it a particularly apposite source of law in a time of seismic shifts in the distribution of power within a vastly diverse community of States, when a new global order is expected to emerge, the contours of which are not yet clearly discernible. This book applies general concepts of legal philosophy to explain the continuing relevance of custom as a source of international law while at the same time inferring from this theoretical framework concrete practical and methodological consequences, the most important of which is the special role that purposive interpretation plays with respect to rules of international custom. Given this broad approach, the book will be of interest to several groups of potential readers including academics interested in the philosophy of customary law in general, academic international lawyers and legal practitioners, especially judges, scholars of international relations and all those interested in how the international community of States organises itself.