Abstract The ECJ has long asserted its Kompetenz-Kompetenz (the question of who has the authority to decide where the borders of EU authority end) based on the Union treaties which have always defined its role as the final interpreter of EU law. Yet, no national constitutional court has accepted this position, and in its Lisbon Judgment of 2009 the German Constitutional Court (FCC) has asserted its own jurisdiction of the final resort' to review future EU treaty changes and transfers of powers to the EU on two grounds: (i) ultra vires review, and (ii) identity review. The FCC justifies its claim to constitutional review with reference to its role as guardian of the national constitution whose requirements will constrain the integration process as a standing proviso and limitation on all transfers of national power to the EU for as long as the EU has not acquired the indispensable core of sovereignty, i.e. autochthonous law-making under its own sovereign powers and constitution, and instead continues to derive its own power from the Member States under the principle of conferral. Formally therefore, at least until such time, the problem of Kompetenz-Kompetenz affords of no solution. It can only be 'managed', which requires the mutual forbearance of both the ECJ and FCC which both claim the ultimate jurisdiction to decide the limits of the EU's powers—a prerogative which, if asserted by both parties without political sensitivity, would inevitably result in a constitutional crisis. The fact that no such crisis has occurred, illustrates the astute political acumen of both the FCC and the ECJ.