There is a common refrain, in US and UK legal writing, that an assertive exercise of judicial power particularly in matters of national security jeopardizes established institutional arrangements, most especially democratic accountability. When courts take the reins, the legislature loses the incentive to act and provide political/democratic checks on executive power. As the division between the national and the international becomes increasingly complex there is greater strain on the institutional public law principles underpinning judicial and legislative authority—in this case the values of articulated governance and that of democratic legitimacy. In this paper I ask two distinct but related questions. Can judicial review prompt legislative engagement? And, what can the theory underlying the doctrine of the separation of powers tell us about what legitimate judicial and legislative action looks like in this arena?