Brexit ruling to be delivered by Supreme court on 24 January

11 justices will create panel to resolve whether the government can formally initiate article 50 without parliamentary approval

A brief summary of the decision will be read out at 9.30am on Tuesday. Photograph: Adrian Dennis/AFP/Getty Images

The supreme court will deliver its eagerly awaited judgement next Tuesday on whether ministers or parliament have the legal authority to trigger Brexit.

The court’s president, Lord Neuberger, will read out a brief summary of the decision at 9.30am on 24 January. Lawyers for the main parties will have received advance notice shortly beforehand.

The ruling by the 11 justices will resolve whether the government, through its inherited use of royal prerogative powers, can formally initiate article 50 of the treaty on European Union (TEU) without the explicit approval of MPs and peers.

Article 50 begins the process of the UK’s withdrawal from the EU. If a majority of justices decide, as is widely expected, that parliamentary support is required, then the judgement is expected to specify that a legislative act is needed.

Devolved assemblies in Edinburgh, Cardiff and Belfast will also read the judgement closely to see whether it grants them any procedural or consultative role in the process of triggering Brexit. The judgement will test the significance of the Sewel convention, which says that if Westminster is introducing legislation on issues that have been devolved it “normally” has to seek the consent of the devolved parliaments.

The panel of 11 justices is the largest ever assembled for a single case since the law lords were created in 1876. Such judicial mass mobilisation is recognition of the constitutional significance and political sensitivity of the hearing. The court normally sits in panels of five; an odd number is always required to ensure there cannot be a tie.

Article 50 of the TEU states that any member state may leave “in accordance with its own constitutional requirements”, an undefined term that has allowed the two sides to pursue rival interpretations. The case has opened deep rifts in the consensus over the UK’s unwritten constitution.

The case was conducted on the basis that article 50, and therefore Brexit, cannot be reversed once begun. A separate legal challenge is due to take place in Dublin this spring to test its revocability. Another is due to be heard in London to establish whether the UK automatically quits the single market or European Economic Area when it leaves the EU.

The lead claimant in the supreme court case is the investment manager Gina Miller. Miller, who says she has received death threats, has said her case is about asserting parliamentary sovereignty and not an attempt to reverse Brexit. Another claim was brought by a London hairdresser, Deir Dos Santos.

The reading of the summary by Neuberger is expected to last only five minutes. The proceedings will be broadcast live on the supreme court’s website. Lead counsel from the main parties will be given sight of the judgement an hour and a half in advance of its delivery.

The full judgment will be put online at around 9.35am. The court’s judgement may be divided into several sections depending on whether or not individual justices choose to deliver dissenting – or concurring judgements stressing different aspects of the ruling.

Draft versions of judgements are often circulated to parties involved in a case several days beforehand. Government sources have already signalled that they expect to lose the main point of their appeal and have begun drafting versions of a bill to put before parliament approving Brexit.

Fair Deal for Expats is one of the claimants in the case. Its chairman, John Shaw, said: “Fair Deal for Expats eagerly awaits the judgement of the supreme court. [Our] members have been involved in this case from the outset, standing up for the 2 million British people who live in other EU countries. Many of them were not allowed to vote in the referendum, yet they count among those most profoundly affected.

“It’s of the utmost importance to those people that a proper debate takes place in parliament about their future and they’re not sidelined in a rush to give notice under article 50, without knowing what the future holds for them. We hope that the government ensures that it does everything it can to protect British citizens in the EU and their families, whatever the outcome of the case.”

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