The practice of law has been challenged by the promulgation of transnational norms associated with “corporate social responsibility” (“CSR”), arising beyond the State, with little or no connection to traditional sources of positive law. These phenomena, which we will refer to as “transnational CSR norms,” are increasingly important guides to behaviour for corporate actors, despite the fact that adherence to such norms is not “required” by positive legal systems. Perhaps for this reason, transnational CSR norms are typically poorly understood and possibly underutilized in the practice of law. The purpose of this paper will be to determine, by recourse to legal theory, whether, and if so how, transnational CSR norms may be related to positive legal systems, and therefore to the practice of law. In so doing, we will seek to develop a theoretical understanding of the role transnational CSR norms can, do, and ought to play within processes of legal reasoning, particularly from the theoretical starting points offered by analytical/ positivist, and discursive theories of law.