Law is constantly caught between stasis and dynamism, between the production of legal certainty and the adaptation to a changing environment. The tension between both is particularly acute in international law, given the absence of legislative mechanisms on the international level and the high doctrinal thresholds for change through treaties or customary law. Despite this apparent tendency towards stasis, international law is changing frequently and rapidly in many areas, though in ways that are not well understood. This article seeks to begin an inquiry into these ways of change, starting from two vignettes of recent change processes and presenting a number of conjectures about core elements of a conceptualization of change in international law. The resulting picture reflects significant variation across different areas of international law, multiple paths of change outside traditional categories, and states in different—and not always central—roles. Much change observed in contemporary international law travels on paths and is advanced by authorities created by social actors and their practices relatively independently from doctrinal representations. This presents a challenge for doctrinal categories, and it should provoke a broader, empirical reconstruction of the social life of international law today—a far more dynamic but also less orderly life than typically assumed.