In R. (Miller) v Secretary of State for Exiting the European Union, the Supreme Court of the UK (1) held that the UK Government had no prerogative power to initiate the formal process whereby the UK will withdraw from the EU and (2) declined to recognise any requirement that the devolved legislatures’ consent be obtained in respect of legislation authorising the Government to commence the withdrawal process. This article critically examines Miller, arguing that the majority's analysis veers between unwarranted muscularity in relation to the prerogative issue and unnecessary conservatism as regards the devolution issue. The article goes on to argue that while the majority judgment's restrictive approach to the prerogative may be viewed as a progressive victory for constitutional principle, such an evaluation can be sustained only if a set of relatively traditional constitutional premises are adopted to begin with. The article also contends that the general approach adopted by the majority is problematic, given its willingness to invoke arguments of constitutional principle without adequately engaging with questions about what the pertinent principles are, and argues that such an intellectually lackadaisical mode of constitutional adjudication is to be deprecated.