Can multilateral treaties succeed in reshaping expectations and changing behaviour when they are rejected by the most powerful states in the international system? In the past two decades, coalitions of “middle power” states and transnational civil society groups have negotiated binding legal agreements on topics including disarmament, international criminal justice, and environmental protection, in the face of concerted opposition from China, Russia, and—most especially—the United States. These instances of a so-called “new diplomacy” reflect a deliberate attempt to use the language of international law to bypass great power objections and establish binding global standards. Critics have frequently derided such efforts as utopian and counter-productive because the treaties failed to meet the approval of those states that allegedly possess the military, economic, and diplomatic resources to most effectively manage complex international cooperation.

The absence of the US and other leading states from legal institutions thus holds consequences for international relations that deserve detailed analysis; yet thus far no study has offered a systematic, comparative study of the promise, and limits, of multilateralism without the great powers. This book addresses this gap by developing a novel theoretical account of international legal efficacy under conditions of great power ambivalence, and applying this framework to evaluate the implementation of two archetypal cases, the Antipersonnel Mine Ban and International Criminal Court. It demonstrates that both treaties have substantially reshaped conduct in their respective domains, but with important variation in the extent and breadth of their impact. This finding provides the impetus for considering the prospective suitability of adopting a similar strategy in other areas of contemporary concern. This book is well placed to offer a timely addition to a dynamic and growing literature on the practice and consequences of international governance. It should therefore appeal to academics, civil society experts, and foreign policy practitioners interested in a range of global challenges in fields such as security, human rights, and the environment.