Double‐Edged Bandwagon Effects in International Law—Rationalist and Behavioral Explanations

This article examines bandwagon effects in international law by integrating rationalist and behavioral perspectives. While the diffusion of treaties and norms has often been understood as a progressive process leading to broader participation and compliance, states also imitate negative examples, resulting in treaty withdrawals, non‐compliance, resistance, and sovereigntist narratives. The article distinguishes between participatory and compliance bandwagons and shows that each may develop in either a positive or a negative direction. Rationalist theories explain many of these dynamics through changing incentives, strategic interaction, and collective action problems. Complementing these accounts, the article draws on insights from behavioral economics and social psychology to argue that state behavior is also shaped by bounded rationality, social proof, conformity, framing, loss aversion, and narratives, particularly under conditions of uncertainty. Rather than competing with rationalist explanations, behavioral mechanisms help explain how strategic incentives are perceived, interpreted, and socially transmitted, thereby reinforcing or weakening bandwagon dynamics. The article develops a framework of testable propositions identifying the conditions under which rationalist and behavioral mechanisms are expected to play a greater explanatory role and discusses the implications for the design of international legal institutions.