Harmonization is an essential instrument of international risk governance. It is the process through which disparities among national regulatory standards are ironed out, producing uniform outcomes that all participants in a regime can accept and that facilitate the free exchange of regulated goods in commerce. Contrary to conventional belief, however, harmonization requires not only technical but also political cooperation, since standards themselves are not direct mirrors of reality but are co-produced responses to technoscientific and political uncertainty. Attempts to harmonize standards across national borders therefore pit alternative political cultures and their systems of public reasoning against one another. Put differently, harmonization calls into question the underlying models of subsidiarity that provide the foundation for robust international regimes. This paper examines three models of epistemic subsidiarity – coexistence, cosmopolitanism, and constitutionalism – and discusses each scheme's capacity to protect a nation's fundamental political commitments while advancing the goals of international risk governance.