"Security is a concept routinely invoked in international law, but rarely analyzed closely. Hitoshi Nasu's work in this space has long been innovative and interesting. In this book he systematically unpacks a concept often taken for granted, with illuminating and sometimes surprising results."

"Security has not been studied comprehensively as a concept in international law and yet it clearly is a crucial element in the international legal order, not only shaping foundational constitutional texts such as the UN Charter but operating in a substantive way in a myriad of other sub-fields of international law, for example those governing trade maritime matters, the environment, and human rights. This book makes a profound contribution to developing the study of security in international law as a distinct area of study, not in the sense of a sub-field of international law, but as cross-cutting issue that has significant implications for all sub-fields. It does so by drawing on a wider theoretical lens, through a doctrinal analysis, followed by a detailed assessment of the relevant jurisprudence…The analysis is careful, clear, balanced and rigorous, and is supported by extensive evidence drawn from primary and secondary sources."

"In this fascinating book, West Point's Hitoshi Nasu leads us through the complex, and often fraught, relationship between security and international law. Ambitiously moving beyond specific security challenges, he identifies three generalized criteria for evaluating security threats and determining the appropriate responses to them – good faith, legality, and proportionality. The Concept of Security in International Law is a sophisticated, insightful, and convincing tour de force lying at the intersection of international security and law. A "must read" for those working in either field."