Enjoying control over knowledge production, epistemic communities are central to international politics in guiding decision-maker learning. Yet, we do not understand fully the extent of epistemic community influence on diverse issue areas and the ways in which they drive international regimes. To illustrate an epistemic community’s impact, we investigate the role of experts in the EU, the OSCE and the Council of Europe within the European minority rights regime. Conceptually, we argue that a hierarchy among experts matters for the epistemic community’s influence via policy innovation, diffusion and persistence. Empirically, we track the operation of these mechanisms in the context of EU enlargement as experts on minority rights influence standard-setting, monitoring and standard expansion.