Eighteen months on from the Supreme Court’s judgment in R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5, a good deal has happened in the world of Brexit. However, a good deal has also stayed the same. At its core, the Miller case raised a fundamental question about the respective roles of Parliament and the Executive — a question that has proven to be a running constitutional sore in the Brexit context, as illustrated most recently by the controversy about whether (and if so how) the European Union (Withdrawal) Act 2018 should provide for a ‘meaningful’ parliamentary vote on the terms of withdrawal.

As readers of this blog will be well aware, the Supreme Court ruled in Miller that the Executive, following the referendum of June 2016, did not have prerogative authority to trigger the process, provided for by Article 50 of the Treaty on European Union, whereby Member States may withdraw from the European Union. It followed that the Article 50 process could only be initiated once Parliament had authorised it — which Parliament duly and rapidly did by enacting the European Union (Notification of Withdrawal) Act 2017.

In ruling as it did, the Supreme Court engaged with a set of foundational and interlocking constitutional questions concerning, among other things, the relative powers of Parliament and the Government, the relationship between Westminster and the devolved legislatures, and the extent to which EU membership has changed the UK’s constitution. The judgment also provides further evidence of the Supreme Court’s developing role as a constitutional court, the UK’s lack of a codified constitution notwithstanding.

Readers of Public Law for Everyone can order The UK Constitution After Miller: Brexit and Beyond with a 20 per cent discount. To take advantage of this offer, you will need to order the book via the Hart Publishing website and use the discount code ‘CV7’.

The opening chapter, written by the editors, undertakes a detailed examination of the arguments advanced and the judgments rendered in Miller, at both Divisional Court and Supreme Court levels, as well as identifying a set of noteworthy issues raised by the litigation, including the way in which public engagement was facilitated, the role played by crowdfunding and the approach adopted by the Supreme Court to its constitutional adjudication function.

This is followed by a pair of chapters considering Miller’s implications for the prerogative and judicial control thereof: in his chapter, Jack Williams argues that there are four elements of the control over prerogative powers — ‘existence’, ‘extent’, ‘exclusion’ and ‘exercise’ and that this analytical framework can be can discerned in the Miller decision. Williams critiques competing approaches to the central issue in Miller, arguing in particular that the ‘ambulatory thesis’ of the dissenting Justices does not withstand analysis. Meanwhile, Anne Twomey’s focus is on Miller’s impact on the prerogative more generally; she argues, for instance, that the Supreme Court failed to acknowledge the existence of legislative as well as executive prerogative powers, and that this omission casts doubt upon the Court’s broad assertions concerning the inability of prerogative powers to change domestic law.

A second set of chapters concentrate on the issues raised byMiller concerning the relationship between domestic and EU/international law. Eirik Bjørge considers what light, if any, Millermight shed upon UK courts’ conception of dualism, concluding that the Supreme Court’s judgment nods towards rival understandings based respectively upon parliamentary sovereignty and the protection of individual rights, while failing to arrive at a clear view such that Miller’s legacy in this sphere is an uncertain one. Paul Craig focusses specifically on the relationship between UK and EU law. He considers whether Miller should be understood as having fundamentally reconceptualised that relationship or as reflecting receiving understandings. He concludes that Miller is best seen in this regard as representing continuity with the status quo. David Howarth also considers the relationship between EU and UK law, focussing on how EU law rights and obligations acquired legal force in the UK. Using two contrasting conceptual models, he argues that the Supreme Court in Miller proceeded from a mistaken premise by assuming that EU rights will (by default) be extinguished by Brexit, whereas, according to Howarth, the Court ought to have treated such rights as capable of surviving Brexit — on which view the triggering of Article 50 had far more modest effects than the Court presumed.

In their respective contributions to the book, Aileen McHarg and Gordon Anthony examine Miller’s implications for the UK’s territorial constitution. McHarg concentrates on Miller’s treatment of the Sewel Convention, particularly as regards its impact on Scotland. She is critical of the Supreme Court’s refusal to determine the scope of, or to enforce, the Convention, arguing that the ‘constitutional requirements’ referred to in Article 50 could extend to conventional as well as legal requirements and that the Court is, more generally, guilty of an unduly narrow approach to conventions. In that regard, she contrasts Millerwith instances in which courts have in the past been willing to enforce conventions indirectly, if not directly. Anthony, meanwhile, focuses on the Northern Ireland dimension of Miller, with particular reference to the Agnew andMcCord cases, the appeals in which were joined with Miller in the Supreme Court. Anthony is critical of several aspects of the Supreme Court’s judgment, suggesting that it signals a potential u-turn from the recognition in the Robinson case of the specific constitutional importance of the Northern Ireland Act 1998, and arguing that the Court failed adequately to engage with issues arising from the Sewel Convention. He also addresses the longer-term implications of Brexit for the UK’s territorial constitution, with particular reference to the distribution of power under what is now the EU (Withdrawal) Act 2018.

Sir John Laws and Mark Elliott each examine, in different respects, what light the Millercase, and EU membership more generally, cast upon our understanding of domestic constitutional law and, in particular, its hierarchical ordering. Sir John’s primary focus is on the notion of ‘constitutional statutes’ — a notion that he notably introduced in his judgment in the Thoburn case — and on whether, and if so how, Miller relies upon or develops this category. He argues that in Miller the Supreme Court majority did not directly rely upon the constitutional status of the European Communities Act 1972, and that this omission led it into error when it sought to conceptualise the place that EU law has enjoyed in the domestic legal hierarchy. In his chapter, Elliott critiques the notion of constitutional statutes, arguing that the binary choices it presents between ‘constitutional’ and ordinary legislation, and between express and implied modes of repeal, are too stark, and that these choices failure to capture and reflect the subtle and complex nature of the UK constitution, its interplay between the judicial and the political roles, and its preference, on occasion, for constructive ambiguity over conceptual clarity.

The closing chapters of the book examine Miller in broader perspective. In their contribution, Richard Ekins and Graham Gee consider the political context and consequences of the decision. Among other things, they argue that the Supreme Court majority strayed from the judiciary’s proper constitutional role by adopting a reading of the European Communities Act 1972 that the majority believed to be constitutionally proper but what was not legally sound. Against this background, Ekins and Gee caution against the increasing politicisation of the legal process as more litigation is undertaken for what they characterise as political motives. In her chapter, Alison L Young explores the potential implications of Miller for the future of constitutional adjudication in the UK. She observes that the Supreme Court majority adopted a relatively deductive approach, whereby it was willing to reason ‘down’ from broad constitutional principles, but argues that this is not novel, and can be discerned in other apex-level judgments in the UK. Young also argues that while the Court might be said to have ruled on a ‘moot’ question (because no notification had, by the time of the judgment, been issued under Article 50), doing so in appropriate circumstances represents sound constitutional policy reflecting a precautionary principle that anticipates constitutional problems. Young concludes by considering whether such ‘abstract’ constitutional review might require procedural innovation, such as the ‘reference procedures’ found in, for instance, the Canadian constitution.

As this volume shows, the Miller case, as well as occupying a key place in the early legal history of the UK’s departure from the EU, raises fundamental questions about the nature of the British constitution and its future development. Indeed, the case has served to shine a light on the UK’s modern constitutional order, identifying crucial areas of uncertainty and contention, as well as issues that will need to be thought about further — both by law-makers and by scholars — as the UK constitution continues to develop during the Brexit process and beyond.

The UK Constitution After Miller: Brexit and Beyond, co-edited by Mark Elliott, Jack Williams and Alison L Young,is published by Hart Publishing, an imprint of Bloomsbury. For further information about this book and how to purchase, please refer to the Hart Publishing website. Mark Elliott is Professor of Public Law at the University of Cambridge and a Fellow of St Catharine’s College, Cambridge. Jack Williams is a barrister at Monckton Chambers. Alison L Young is the Sir David Williams Professor of Public Law at the University of Cambridge and a Fellow of Robinson College, Cambridge.