This article argues that the rise of transnational regulation has a transformative impact on law. It examines the field of transnational environmental regulation to show that its proliferation challenges the continued appropriateness of representations of law as (i) territorial, (ii) emanating from the state, (iii) composed of a public and private sphere, (iv) constitutive and regulatory in function, and (v) cohesive and regimented. Instead, law is increasingly perceived as (i) delocalized, (ii) flowing from a plurality of sources, (iii) organizationally inchoate, (iv) reflexive and coordinating in function, and (v) polycentric. Together, these shifts in perception amount to a transformation that the article identifies as the transnationalization of law. The article then explores three responses to the transnationalization of law. It distinguishes responses motivated by a desire to reclaim the traditional conception of law from those that seek to reconstruct law at the transnational level and responses that advocate a context-responsive reconceptualization of law. Each response, it will be shown, creates a different set of opportunities for, and challenges to, the relevance of law for transnational regulation.