Abstract The European Court of Justice's (ECJ's) jurisprudence of fundamental rights in cases such as Schmidberger and Omega extends the court's jurisdiction in ways that compete with that of Member States in matters of visceral concern. And just as the Member States require a guarantee that the ECJ respect fundamental rights rooted in national tradition, so the ECJ insists that international organisations respect rights constitutive of the EU. The demand of such guarantees reproduces between the ECJ and the international order the kinds of conflicting jurisdictional claims that have shadowed the relation between the ECJ and the courts of the Member States. This article argues that the clash of jurisdiction is being resolved by the formation of a novel order of coordinate constitutionalism in which Member States, the ECJ, the European Court of Human Rights and other international tribunals or organisations agree to defer to one another's decisions, provided those decisions respect mutually agreed essentials. This coordinate order extends constitutionalism beyond its home territory in the nation state through a jurisprudence of mutual monitoring and peer review that carefully builds on national constitutional traditions, but does not create a new, encompassing sovereign entity. The doctrinal instruments by which the plural constitutional orders are, in this way, profoundly linked without being integrated are variants of the familiar Solange principles of the German Constitutional Court, by which each legal order accepts the decisions of the others, even if another decision would have been more consistent with the national constitution tradition, 'so long as' those decisions do not systematically violate its own understanding of constitutional essentials. The article presents the coordinate constitutional order being created by this broad application of the Solange doctrine as an instance, and practical development, of what Rawls called an overlapping consensus: agreement on fundamental commitments of principle—those essentials which each order requires the others to respect—does not rest on mutual agreement on any single, comprehensive moral doctrine embracing ideas of human dignity, individuality or the like. It is precisely because the actors of each order acknowledge these persistent differences, and their continuing influence on the interpretation of shared commitments in particular conflicts, that they reserve the right to interpret essential principles, within broad and shared limits, and accord this right to others. The embrace of variants of the Solange principles by many coordinate courts, in obligating each to monitor the others' respect for essentials, creates an institutional mechanism for articulating and adjusting the practical meaning of the overlapping consensus.