Commentary – UK Supreme Court rules Parliament must approve Brexit notification

January 25, 2017

Today the UK Supreme Court ruled, by an 8-to-3 vote, that an Act of Parliament is required to authorize the government to notify the European Council of its intention to withdraw from the European Union. The decision affirms the ruling of the High Court of Justice in November that, because an exit from the EU would deprive British citizens of rights under EU law and because the government’s “prerogative powers” can’t be used to change domestic law, the government can’t base its notification on those powers and must instead obtain the prior approval of Parliament.

In 2007, the EU’s Treaty of Lisbon, which amended the Treaty on European Union and took effect in 2009, provided member states for the first time with the possibility of withdrawing from the EU. Article 50 of the treaty says a member state may decide to withdraw “in accordance with its own constitutional requirements.” It goes on to say that a member state that has decided to withdraw shall notify the European Council, which consists of the heads of state or government of the member states, of its intention, after which the EU, in light of guidelines provided by the council, shall negotiate and conclude an agreement with the state that sets out the arrangements for its withdrawal, taking account of the framework for its future relationship with the EU. It stipulates that the EU treaties shall cease to apply to the withdrawing member state from the date of entry into force of the withdrawal agreement or, failing that, two years after the notification unless the council unanimously agrees to extend the period.

Although 52 per cent of those voting in the June 23rd referendum voted to leave the EU, a large majority of the UK House of Commons – indeed, almost 75 per cent of the Members of Parliament, including more than half of the Conservative M.P.s, were on record prior to the referendum as supporting the Remain option. 

Although she supported the Remain option, Theresa May believed her government should abide by the vote in the referendum; the problem, of course, was that with a narrow working majority in the House, it was far from certain the government could obtain a majority in support of a motion to notify the European Council of the UK’s intention to withdraw to a vote. So it decided to dispense with a parliamentary vote and simply use its “prerogative powers” to notify the EU of its intention to withdraw.

After the referendum, a number of individuals filed claims before the High Court arguing that the principle of parliamentary sovereignty and the loss of rights under European law if the UK were to leave the EU required that notification of the intention to withdraw be approved by Parliament. In November, the High Court ruled in favor of those claimants and the government immediately appealed to the Supreme Court.

The claimants were right for several reasons. For one thing, Article 50 stipulates that a state’s decision to withdraw be made “in accordance with its own constitutional requirements.” A decision supported by 37 per cent of the electorate – 52 per cent of the voters in the referendum supported the Leave alternative and 72 per cent of the electorate participated in it– in a referendum could hardly be regarded, in a country in which parliamentary sovereignty is the bedrock principle of its unwritten constitution, as being “in accordance with its own constitutional requirements.”

For another, Article 50 makes it clear that once the UK notifies the EU of its intention to withdraw, the two-year clock will start counting down toward an exit, even without a withdrawal agreement, unless all 27 continuing members of the EU agree to extend the negotiation.  As a result, the notification could very well trigger a process resulting in an exit, with or without a withdrawal agreement, at the end of the two-year period.  For the High Court and now the Supreme Court, the government’s claim that it could embark on a process that could lead to an exit from the EU on unfavorable terms or no terms at all without the prior approval of parliament did not comply with that bedrock principle of parliamentary sovereignty.

Prime Minister May announced several months ago that the UK would notify the European Council of its intention to withdraw by the end of March.  In early December, while the Supreme Court was hearing the case, the House of Commons approved, by an overwhelming margin – 448 to 75 – an amended motion that called on the prime minister to publish the government’s plan for leaving the EU before Article 50 is invoked and called on the government to invoke Article 50 by the end of March.  And last week, in a major address, the prime minister set out the government’s objectives in the negotiations with the EU that will follow after the Article 50 notification.

Given the December vote and last week’s speech, it’s probably the case that Parliament will in due course – and possibly before the end of March – enact an Act authorizing the government to notify the EU of the UK’s intention to withdraw. But today’s Supreme Court decision will at least require the government to formally present, defend, and obtain approval of its plan for Brexit in both the House of Commons and House of Lords – which, in a country that adheres to the principle of parliamentary sovereignty, is at it should be.


David R. Cameron is a professor of Political Science and the director of the Program in European Union Studies.