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.

'In its totality, Customary International Law in Times of Fundamental Change: Recognizing Grotian Moments is a stimulating and challenging examination of how pivotal moments in history can precipitously affect the field of customary international law and international relations. At its best, this book has the potential to influence international law scholars who are deeply entrenched in their own views and spark interest in students of the law who have not yet embarked on their intellectual journeys.'

Source: George Washington International Law Review

'Professor Scharf examines the concept of the ‘Grotian Moment’, providing a critical yet thought-provoking analysis of the instances in which customary international law can, and indeed does, develop with surprising rapidity and limited state practice. Professor Scharf ’s contribution is widely set to leave its mark, as acknowledged by the authoritative list of names endorsing the book.'

Jonathan Worboys Source: King's Law Journal

'… this is an excellent book. It is clearly and engagingly written (as anyone familiar with Scharf’s previous work would expect). The research underpinning it is similarly faultless. Moreover, it is short and to the point: its arguments are both concisely made and precisely targeted. This book is ultimately an extremely important addition to the literature. Its thesis is at the same time indisputable (in and of itself) and yet highly contestable both in terms of its framing and application to specific examples. Customary International Law in Times of Fundamental Change will undoubtedly spark important debate and further research on the process of expedited custom: a process that is controversial and potentially dangerous, but which - as Scharf ably demonstrates - undeniably occurs.'

James A. Green Source: International and Comparative Law Quarterly