International institutions have proliferated rapidly in the postwar period. As new problems have risen on the international agenda, the demand for international regimes has followed. At the same time, international norms have become more demanding and intrusive. Governance systems dominated by elites have given way to more participatory modes; the policy process has become more complex as a growing array of [actors] become engaged in decision making.

These trends – in particular the rising density of international institutions – make it increasingly difficult to isolate and “decompose” individual international institutions for study. Yet efforts to build and test theories about the origins, operation, and influence of international regimes have typically been conducted as though such decomposition was feasible. Most empirical studies focus on the development of a single regime, usually centered on a core international agreement and administered by a discrete organization. Such studies occasionally note the complicated links among international institutions, but [do not focus] systematically on explaining institutional “interplay.” A few studies have explored institutional interactions in hierarchical or nested regimes in which certain rules have explicit precedence over others, but the theoretical implications are limited because international agreements are rarely hierarchical. The prevailing scholarship on regimes has also taken a functional approach to analyzing cooperation and has not given close attention to how the legal and intellectual framing of issues affects the boundaries of regimes.