Humanity in the twenty-first century faces serious global challenges and crises, including pandemics, nuclear proliferation, violent extremism, refugee migration, and climate change. None of these calamities can be averted without robust international cooperation. Yet, national leaders often assume that because their states are sovereign under international law, they are free to opt in or out of international cooperation as they see fit. This book challenges conventional wisdom by showing that international law requires states to cooperate with one another to address matters of international concern-even in the absence of treaty-based obligations. Within the past several decades, requirements to cooperate have become firmly embedded in the international legal regimes governing oceans, transboundary rivers, disputed territories, pollution, international security, and human rights, among other topics. Whenever states address matters of common concern, international law requires that they work together as good neighbors for their mutual benefit. This title is also available as Open Access on Cambridge Core.

‘Criddle and Fox-Decent suggest an intriguing possibility: that over the last century an obligation of cooperation has emerged in international law, an obligation that permeates international law today. Required reading in daunting times.'

Frédéric Mégret - Professor and Hans & Tamar Oppenheimer Chair in Public International Law, McGill University

‘Exhibiting an impressive breadth of historical and legal scholarship, Criddle and Fox-Decent's carefully argued account of international law inspires at a time when hope is in high demand but in short supply.'

Andreas Føllesdal - Professor of Political Philosophy, University of Oslo