Abstract: This working paper 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) delocalised, (ii) flowing from a plurality of sources, (iii) organisationally inchoate, (iv) reflexive and coordinating in function, and (v) polycentric. Together, these shifts in perception amount to a transformation that the paper identifies as the transnationalisation of law. The paper then explores three responses to the transnationalisation 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, thirdly, responses that advocate a context-responsive reconceptualisation 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.