The involvement of national courts in EU treaty making was once controversial, but it is now commonplace. This chapter takes a closer look at the rise of courts at the consent stage of EU treaty making. It provides a detailed examination of changing constitutional rules and norms concerning the prior constitutional review of treaties in each of the EU’s twenty-eight member states. This analysis focuses, in particular, on the question of who, if anyone, can trigger such reviews. On the basis of this analysis, we present the third of our three ratification scales.