Norm research has struggled to leave behind its liberal progressive perspective on norms. It has turned its attention towards contestation and norms erosion. Still, in a number of studies contestation is not merely an analytic concept but a normative concept as well, describing a problematic development of norms. Plainly, contestation is often seen as a form of political backlash. This is problematic because the bulk of normative change proceeds in the form of contestation, so we need to be able to distinguish the two. Studying the recurring and radicalising contestation of the International Criminal Court, this article demonstrates the intimate relationship between contestation and backlash. It argues that while backlash might be fruitfully applied to the study of norm contestation, its added value for norms research is linked to the normative connotation of regressive politics, that is, a ‘thick’ concept of backlash.