In its judgment in Miller, the Supreme Court reached two key conclusions: that an Act of Parliament is needed before Brexit can be triggered, and that the law does not enable devolved legislatures in Scotland, Wales or Northern Ireland to block Brexit.
Article 50 of the Treaty on European Union sets out the process whereby Member States can withdraw from the EU. Following the referendum in June 2016, the UK Government indicated that it would trigger the withdrawal process using ‘prerogative’ power — that is, power that the Government holds inherently, rather than power that it has been given by Parliament. The claimant in Miller argued that the Government could not do this, and that Brexit could be triggered only if Parliament enacted legislation allowing withdrawal to be initiated. The core of the claimant’s case was that legislation enacted by Parliament — the European Communities Act 1972 — conferred EU law rights on people in the UK, and that rights granted in that way by Parliament could not be taken away by the Government. In making this argument, claimant relied upon the long-established principle that Parliament’s legal powers are constitutionally superior to the prerogative powers of the Government, and that the latter must therefore yield to the former.
The essence of the Government’s case was that the conduct of foreign relations — including entry into and withdrawal from treaties — is a matter that falls within the prerogative. Withdrawal from the EU treaties was therefore something that could be initiated by the Government using its prerogative authority. Moreover, said the Government, doing so would not cut across what Parliament had done when it enacted the 1972 Act, because Parliament had only ever intended for EU law, and rights granted by it, to be effective in the UK for as long as the UK remained a Member State.
The majority of the Supreme Court rejected the Government’s arguments. It held that EU law had become part of — indeed, a source of — UK law thanks to the 1972 Act. Now that EU law has that status, said the majority, getting rid of it is not a matter of foreign relations, meaning that its removal cannot be accomplished via the foreign relations prerogative. And, said the majority, when Parliament passed the European Communities Act in 1972, it endorsed and gave effect to the UK’s membership of the EU: having intended that the UK should be a member of the EU, Parliament had not intended the Government to be able unilaterally to take the UK out of the EU. The fact that a referendum had taken place and secured a majority in favour of Brexit did not affect this legal analysis: the significance of the referendum, said the Court, was political.
As Lord Pannick QC put it for Mrs Miller, when ministers give Notice they will be “pulling … the trigger which causes the bullet to be fired, with the consequence that the bullet will hit the target and the Treaties will cease to apply”. — Majority judgment
Of the three judges who dissented on the question of whether legislation is needed, Lord Reed gave the fullest judgment. He argued that EU law is not a source of UK law, but is rather a distinct body of law, and that the 1972 Act merely gives effect to EU law in the UK to the extent that the UK’s treaty obligations require. If, said Lord Reed, the UK leaves the EU and therefore no longer has any relevant treaty obligations, that will not cut across the Act. Parliament had not intended that people in the UK should have or retain any particular EU rights, merely that UK and EU law should be aligned for the duration of membership.
On the devolution point, the Court was unanimous. Key to the devolution issue is a ‘constitutional convention’ — that is, a political understanding and agreement about how the constitution operates — known as the ‘Sewel Convention’. According to the Convention, when (among other things) the UK Parliament plans to legislate so as to change the powers of a devolved institution, the relevant devolved legislature must normally consent before the legislation is enacted. Brexit will change the devolved bodies’ powers: at present they must comply with EU law; after Brexit, they will not have to do so. This raises questions about whether the legislation the UK Parliament will now have to enact authorising the triggering of Article 50 attracts the application of the Convention. However, the Supreme Court refused to answer that question. It held that judges ‘are neither the parents nor the guardians of political conventions; they are merely observers’: while they can ‘recognise the operation of a political convention in the context of deciding a legal question’, they cannot ‘give legal rulings on its operation or scope, because those matters are determined within the political world’.
But it had been suggested that the Sewel Convention was no longer just a political convention. That argument was based on the fact that the Scotland Act 2016 — enacted in the wake of the Scottish independence referendum — acknowledges the Convention: it says that it is ‘recognised’ that the UK Parliament ‘will not normally legislate with regard to devolved matters without the consent of the Scottish Parliament’. Did this make the Convention into a law — or at least into something that the Court could adjudicate on? No, said the Supreme Court. The Sewel Convention remained just that — a convention — and therefore not a matter for the Court. That conclusion was unsurprising, and underlines the politically awkward fact that the ‘recognition’ of the Convention by the 2016 Act was of limited relevance: it amounted to a political token, but did not legally enhance the constitutional position of the devolved institutions.
The Supreme Court has thus made it clear that the devolved legislatures lack the legal power to block Brexit. But, the Court has held, the UK Parliament does have that power, because only it can allow Article 50 to be triggered. It must now decide whether, and if so when and on what terms, to authorise the Government to take that step. When the Divisional Court gave judgment in Miller last year, the judges who decided the case were unfairly dubbed the ‘enemies of the people’ by the press. But all the judges have really done is to put the Brexit ball firmly back in Parliament’s court — where the people’s elected representatives will have to decide what happens next.