Abstract This chapter presents an account of the constitutional law of transnational society from a distinctively political perspective. It uses a neoclassical definition of the constitution as the legal norms that frame the actions of a political system to examine and construct constitutional functions that reach beyond the legal systems of nation-states. It advances the thesis that the concept of transnational constitutional law can be applied to three separate legal-political domains in contemporary global society. This concept can be used to analyze constitutional aspects of international law, and it can be applied to national constitutional law, both of which have a strong transnational dimension and are supported by normative elements that are formed through transnational processes. This concept can also be applied to characterize and examine an emergent, conclusively transnational legal order, in which legal formation occurs in more spontaneous and contingent fashion. In each domain, constitutional norms produce an underlying inclusionary structure for distinct political functions in society, and transnational constitutional law is defined, most essentially, by its ability to support the relative autonomy of political exchanges and political interactions.