This chapter focuses on the promises and drawbacks of adapting constitutionalism to institutions designed to promote regional integration in the economic sphere. It argues that while constitutional mechanisms can enhance cooperation by locking in states’ commitments, the fact that regional organizations are tasked with specific policy ends creates a significant departure from the fundamental principles that constitutionalism is traditionally prized for advancing. The chapter develops this argument primarily with reference to the European Union, while noting the limits of generalizing from that case. It argues that the EU’s supranational legal order amplifies a logic germane to any constitutional system, but which has often been overlooked by political theorists. Alongside their better-know functions of facilitating democratic self-rule and safeguarding individual freedom, constitutional systems are also expected to enable the effective exercise of public power. Insofar as regional institutions are designed to help states govern more effectively, particularly in the economic domain, they advance this neglected but essential rationale of constitutional rule. The chapter situates this argument in the context of the burgeoning literature on the non-democratic uses of constitutionalism, showing that constitutional mechanisms can be configured to advance different ends, not all of them emancipatory.