Jeremy Waldron and Jeffrey Goldsworthy (the leading more-or-less abstract and more-or-less doctrinal critics of constitutional review) establish and agree that although Parliament is imperfect, it is nonetheless immeasurably better than the courts as a forum for making political decisions. But both also endorse or defend the further claim that, in the light of this state of affairs, the imperfections of parliament – dwarfed as they are by the imperfections of the courts – are not relevant to the possible justification of constitutional review. Here, in contrast, I propose an account of the nature of constitutional authority under which an inferior authority can still legitimately exercise a power to override or limit a more legitimate authority. Constitutional authority is, I argue, an instance of what I call composite authority. More precisely, I intend to defend some or all of the claims that (i) there is such a thing as composite authority; (ii) constitutional authority is an instance of it; and (iii) it grounds a justification for constitutional review in the UK constitution.