[---] The concept, and intentionally unfamiliar terminology, of ‘contagious lawmaking’ creates a space for both fleshing out, and problematizing, the phenomenon of the dynamic and multi-directional transfer of environmental law ideas. This article sets the stage for further study of the global diffusion of environmental law. It does so by identifying the phenomenon of contagious lawmaking and by making explicit some of the terminological and methodological challenges implicated in its study. The article draws on narratives of the ‘global’ diffusion of environmental impact assessment, cited as ‘the most widely adopted environmental management tool in the world’.