What can we learn about the ‘international’ through the ‘transnational’? This article investigates transnational spaces and practices in the context of international law and their transformative influence on our understanding of the international. I argue that the relationship between the transnational and the international is not dichotomous, but an expression of the shifting location of power and authority in social relations across scales. The article contributes to this special issue by tracing dynamics of actualisation and reification of the international in various literatures. Reviewing uses of the ‘transnational’ in law and International Relations, I first show how the concept was used to unsettle the reason of state that defines both disciplines. The second part explores the relationship of the transnational and international through Bourdieusian studies of international law, in which the transnational is used as a strategic space for action generative of new legal practices and a social space in which actors who hold various capitals participate in shaping international law. Finally, I analyse how international political sociology has unsettled both the transnational and the international through the image of transversal lines cutting across these spaces.