This post was written before the Supreme Court gave its decision in the Miller case. For an overview of the judgment itself, see 1,000 words: The Supreme Court’s Judgment in Miller

The decision of the Supreme Court in Miller — in which the UK Government will ask the Supreme Court to rule that the Article 50 process for withdrawing from the EU can be initiated without parliamentary involvement — may have significant consequences for how Brexit unfolds. But the Court is certainly not being asked to rule upon the wisdom of Brexit. What, then, are the legal issues that the Court is being asked to determine?

The Government wishes to trigger Article 50 using the Crown’s ‘prerogative’, or inherent, power to conduct the foreign relations of the UK. However, the claimant contends that the Government cannot do this. The Divisional Court agreed with the claimant, in effect holding that Article 50 cannot be triggered without an Act of Parliament. Triggering Article 50, it is said, will set in a train a process leading to Brexit, thereby removing from UK citizens the EU law rights that Parliament gave them when it enacted the European Communities Act 1972. And, says the claimant, since it is well-established that the Government cannot use its prerogative power to abrogate or frustrate Acts of Parliament, the prerogative cannot be used to trigger Article 50, since the natural consequence of doing so would be to fundamentally undermine the 1972 Act. It would remain on the statute book, but it would be rendered an empty shell.

The kernel of the Government’s response to this argument is that the 1972 Act does not as such create any rights in national law. Rather, the Act serves as mechanism, or ‘conduit’, whereby EU law rights can be exercised in the UK for as long as the UK remains a member of the EU. On this analysis, the objective of the 1972 Act was never to confer upon UK citizens any particular rights. Rather, its purpose is to make sure that the UK discharges whatever obligations it has at any given time by dint of being an EU Member State. Indeed, the Act explicitly gives legal effect in the UK only to those rights that arise under the EU Treaties ‘from time to time’. Hence the Government contends that triggering Article 50 will not result in the removal of any rights created by an Act of Parliament, and will not undermine the purpose of the 1972 Act. The Act (so the argument goes) was only ever meant to enable the UK to fulfil such obligations as it might have under the EU Treaties; if the UK, due to Brexit, ends up with no such obligations, so be it.

It has been suggested that even if the Government’s argument on this point were to be accepted, its position must founder in the face of the European Parliamentary Elections Act 2002. Unlikely the 1972 Act, the 2002 Act explicitly provides for the right to vote in elections to the European Parliament. That right that will plainly be removed by Brexit, meaning, it is said, that the prerogative cannot be used to trigger Article 50 because that would nullify the right set out in the 2002 Act. A key counterargument, however, is that Parliament could not create — and could not have intended to create — a right to vote in European elections independently of EU membership, meaning that the Act really only confers a right for as long as the UK remains an EU Member State.

Similar issues arise in relation to such rights as free movement. For some, the fact that such rights necessarily go upon Brexit — and cannot be reinstated by new UK legislation — strengthens the claimant’s argument by underlining the rights-removing effect of Brexit. For others, however, this proves the opposite. As Lord Millett, a former Law Lord, has put it, ‘It is a strange right which Parliament can grant and revoke but which, once revoked, it cannot re-enact.’ On this view, such rights were never in the first place ‘granted’ by Parliament, meaning that their removal via Brexit will not undermine any parliamentary legislation.

The litigation before the Supreme Court will incorporate a strand of argument that did not enjoy prominence before the Divisional Court. It concerns the implications of triggering Article 50 for the UK’s devolution settlements — implications that the Supreme Court will have to consider both because it is hearing an appeal against a Northern Ireland case that focussed upon devolution-related matters, and because devolved governments have been given permission to intervene in the case.

Brexit will alter the powers of the devolved legislatures and governments. The devolution legislation enacted by the UK Parliament currently prevents devolved institutions from breaching EU law. But EU law will cease to limit the devolved bodies’ legal powers once Brexit occurs. One of the arguments, therefore, is that Brexit will rob of any effect those provisions in the devolution statutes that say that EU law limits the competence of devolved institutions — and that the prerogative cannot be used to undermine legislation in such a way. It is also said the effect of withdrawal from the EU triggers the ‘Sewel Convention’, according to which the UK Parliament will not normally legislate to (among other things) change a devolved institution’s powers unless the relevant devolved legislature consents.

The Government’s response to the first argument is that references in the devolution legislation to EU law are in effect contingent upon EU membership, which they ‘assume’ but do not ‘require’. As to the second argument, it is unclear that the Sewel Convention is relevant to the question whether the prerogative can be used to trigger Article 50, given that it is normally understood to be pertinent only when the UK Parliament is legislating. And, in any event, conventions — being political understandings rather than laws — cannot on any traditional view be straightforwardly enforced by courts. It is true that the Scotland Act 1998 was amended in 2016 so as to ‘recognise’ the convention, but it is far from certain that that confers upon the convention any legal force.

Whether one finds the various arguments for or against the Government more compelling is perhaps ultimately (at least in part) a matter of perspective that raises questions about the extent to which EU law remains distinct from (or is conversely a part of) domestic law, and about the extent to which traditional analyses of the constitution remain viable in this new era of devolution. For those reasons, the Supreme Court will find it difficult to address the questions raised by Miller without engaging with a set of interlocking and fundamental questions about how the constitution works today. The Court’s judgment will doubtless have significant implications for how Brexit is taken forward. But it will also afford the Court a once-in-a-generation opportunity to shape discourse and thinking about the nature of the contemporary UK constitution.