This article argues that the changing remit of treaty-making, such that treaties can be just as capable of negatively impacting on domestic constitutional values as ordinary legislation, results in it warranting appropriate mechanisms of domestic constitutional review. Constitutional review has become a staple component of modern constitutionalism and one from which treaties should not be exempt. There is a powerful case for constitutional systems to adopt, whether as a matter of express design or practice, both ex ante and ex post constitutional review of treaties and this is so even where a relevant constitutional system does not otherwise use one or either of these forms of constitutional review. Crucially the adoption of such a combined system of review would contribute to ensuring that treaty-making does not escape the salutary reach of domestic constitutionalism which is all the more indispensable in the absence of meaningful international law constraints on the process and substantive content of treaty-making.