The proliferation of environmental agreements is a defining feature of modern international relations that has attracted considerable academic attention. Typically focusing on happy-end stories of policy creation, the cooperation literature often ignores issue areas where policy agreements are absent. Science and International Environmental Policy introduces nonregimes into the study of global governance, and compares successes with failures in the formation of environmental treaties. By exploring collective decisions not to cooperate, it explains why international institutions form but also why, when, and how they do not emerge.