Briefing

Brexit - Supreme Court confirms that Parliament must approve UK's withdrawal from the EU

Posted by: David Fletcher and Kate Allass | Date posted : 24/01/2017

The Supreme Court has today upheld the decision of the High Court and confirmed that the Government must obtain the approval of Parliament before it can give notice to withdraw from the European Union pursuant to Article 50 of the Lisbon Treaty. The judgment (the full text of which can be found here) brings an end to the legal dispute over the extent of the Government's powers to implement Brexit.

The appeal

The Supreme Court decision follows an appeal against the ruling of the High Court of 3 November 2016 in which the Government was defeated.

In the High Court case, the two claimants (Gina Miller and Deir Dos Santos) had successfully challenged the Government's presumption that Theresa May had the power to invoke Article 50 without a vote in Parliament. The basic premise of the claimants' argument was that the Government did not have sufficient authority to decide alone to withdraw from the EU and to unravel rights under EU law which had been incorporated into domestic law. The High Court accepted this argument, and agreed that the proposed course of action would undermine Parliamentary sovereignty.

The appeal hearing took place over four days in early December 2016 before all eleven Lord Justices of the Supreme Court, something which has not happened since 1876.

  • The Government's position. The Government denied that it was seeking to repeal UK parliamentary legislation and maintained that, by virtue of Royal Prerogative, it has an executive power to repeal international treaties, even if that has a consequential impact on domestic law.

    It was argued that ministers have always used their prerogative powers to sign treaties with other countries. Legislation passed by Parliament then puts those treaties into effect; in this particular case, the European Communities Act 1972 (the 1972 Act) put the Lisbon Treaty into effect.

    The Government argued that the 1972 Act is a "conduit'' by which rights and obligations are implemented in the UK, and that by enacting the 1972 Act, Parliament had not intended to stop the Government from exercising its prerogative to make or unmake the underlying treaty. If Parliament had intended to deny ministers the power to withdraw from the Lisbon Treaty, it would (it was argued) have legislated to ensure that power was expressly curtailed. In short, the Government said that the High Court was wrong to have found that new legislation was required in order to trigger Brexit.

    The Government also relied on the vote which was overwhelmingly passed in the Commons on 8 December 2016 calling on the Government "to invoke article 50 by 31 March 2017" as evidence of informal parliamentary support for the Government's plans.
  • The Claimants' position. The Claimants maintained that triggering Article 50 would revoke the legislation which took the UK into Europe, and said it would require an act of Parliament to enable the UK to leave the EU.

    They argued that the use of prerogative powers to undermine Parliamentary sovereignty was unconscionable, and that invoking Article 50 would inevitably destroy rights created by the 1972 Act which – they said – only Parliament should have the power to destroy. They were critical of the Government's failure to prove that ministers had ever had the prerogative power to take away the rights associated with EU membership.

    The Claimants also urged the Supreme Court to focus purely on the legal issues, and to put to one side the reactions of politicians and the press, presumably in acknowledgment of the voluble strident criticism to which the original High Court judges had been subject following their November decision.

The Supreme Court's judgment

By a majority of eight judges to three, the Supreme Court found that:

  • Withdrawal from the EU makes a fundamental change to the UK's constitutional arrangements, by cutting off the source of EU law. The UK constitution requires such changes to be effected by Parliamentary legislation.
  • The fact that withdrawal from the EU would remove some existing domestic rights of UK residents also renders it impermissible for the Government to withdraw from the EU Treaties without prior Parliamentary authority.
  • It would have been open to Parliament when enacting the 1972 Act to authorise ministers to withdraw from the EU Treaties, but clear words would have been required; not only are there no such clear words, but the provisions of the 1972 Act indicate that ministers do not have such power.
  • Subsequent EU-related legislation and events after 1972, including the introduction of Parliamentary controls in relation to decisions made by UK ministers at EU level relating to the competences of the EU or its decision-making processes, but not to the giving of notice under Article 50, are entirely consistent with an assumption by Parliament that no power existed to withdraw from the treaties without a statute authorising that course.
  • The legal significance of the referendum is determined by what Parliament included in the statute authorising it, and that statute simply provided for the referendum to be held without specifying the consequences. The change in the law required to implement the referendum's outcome must be made in the only way permitted by the UK constitution, namely by legislation.

What will the Government do next?

There is no right of appeal against the decision of the Supreme Court. The Government must now obtain Parliamentary approval before invoking Article 50. It must do this by passing a new Act of Parliament which will require the approval of both the House of Commons and the House of Lords.

Having publicly committed itself to a 31 March 2017 deadline through the Commons vote last year the Government has just over nine weeks to explain exactly what Brexit will mean in practice, to disclose details of its negotiating strategy, and to persuade both the House of Commons and the House of Lords to vote in favour of its plans.

Ministers will want to keep to that time frame and it has been suggested that a short bill which is narrowly focussed on Article 50 and difficult for MPs to amend could be rushed through Parliament. However, some commentators have expressed concern at the potential for future legal challenges if a shortform bill (and future Act of Parliament) does not clearly spell out the detail of what Parliament has consented to.

Since the decision was announced, a spokesman for the Prime Minister has reiterated the UK government's commitment to triggering Article 50 by the end of March this year, which indicates an intention to seek Parliamentary approval in the next two months.

Could this derail Brexit?

It's unlikely that when a vote takes place MPs (or indeed the members of the House of Lords) will block the triggering of Article 50 and the commencement of the Brexit negotiations. Whilst there will no doubt be calls for transparency, and heated debate over the precise language of the Brexit bill, most MPs have already said they will respect the outcome of the referendum and will support the bill when it comes to be passed.

In the unlikely event that the House of Commons rejects the Government's Article 50 legislation, the Government may call a second referendum specifying exactly what would happen in the event of a further vote to leave, in order to put itself on a more certain political and constitutional footing. Alternatively, the Government could call an early general election, and a new Government will be voted in on the basis of manifestos which deal explicitly with Brexit and thus with a clearer mandate.

If you require further information on anything covered in this briefing please contact Kate Allass (kate.allass@farrer.co.uk, 020 3375 7220), David Fletcher (david.fletcher@farrer.co.uk, 020 3375 7117) or your usual contact at the firm on 020 3375 7000. Further information can also be found on the Focus on Brexit page on our website

This publication is a general summary of the law. It should not replace legal advice tailored to your specific circumstances.

© Farrer & Co LLP, January 2017