Constraints on the domestic separation of powers by supranational courts

Abstract

This article examines how supranational courts constrain and shape the separation of powers within their respective contracting parties. It argues that this represents a significant and underexplored development in separation-of-powers theory—one with global reach but little recognition thus far in legal and political science literature. Drawing on a novel analysis of the case law of four supranational courts—the European Court of Human Rights, the European Court of Justice, the Inter-American Court of Human Rights, and the African Court on Human and Peoples’ Rights—it demonstrates how these courts have significantly limited the discretion of contracting states in structuring their domestic separation of powers across all three dimensions: functions, institutions, and personnel, as well as their checks and balances. Taken together, the courts’ jurisprudence increasingly amounts to a supranational blueprint governing the permissible configuration of inter-branch relations. This conclusion carries important theoretical consequences and compels a reconsideration of the principle of separation of powers in a multilevel constitutional order. The article explores how this evolving supranational role might be integrated into our understanding of domestic governance structures and concludes by offering a normative account of the role these courts ought to play in policing the domestic separation of powers.