The rise of international regime complexity

The signature feature of twenty-first-century international cooperation is arguably not the regime but the regime complex. A regime complex is an array of partially overlapping and nonhierarchical institutions that includes more than one international agreement or authority. The institutions and agreements may be functional or territorial in nature. International regime complexity refers to international political systems of global governance that emerge because of the coexistence of rule density and regime complexes. This article highlights insights and questions that emerge from the last 15 years of scholarship on the politics of international regime complexity, explaining why regime complexes arise, what factors sustain them, and the range of political effects regime complexity creates. Our conclusion explains why, in a post-American world order, the trend of greater international regime complexity will likely accelerate.