A crucial aspect of international law is to provide long-term stability and legal certainty. This function presumes that international law-making creates discrete norms and institutions that remain static until they are changed (or replaced) by other discrete institutions. This paper adopts a different point of departure to think about ‘temporariness’. It suggests a dynamic of norm creation and institutional change in global governance. Neither norms nor institutions remain static once they become ‘permanent’. They adapt, evolve and transform. This contribution argues that this process of change is driven by interaction among institutions and actors, which is the default technology of post-national rule-making. How to start thinking about such interaction? What is the added value of focusing on the process of interaction and not on the allegedly static characteristics of actors themselves? How can this approach provide a different normative and critical framework to think about debates on global governance? In answering these questions, this chapter will explore the interaction between international institutions in order to develop the central tenets of a methodology to think about institutional change in post-national rule-making.