Brexit: Supreme Court says Parliament must give Article 50 go-ahead
(about 2 hours later)
The Supreme Court is due to rule on whether Parliament or ministers have the power to begin the Brexit process.
Parliament must vote on whether the government can start the Brexit process, the Supreme Court has ruled.
The landmark judgement, to be announced at 09:30 GMT, will decide how the EU's Article 50 exit clause is triggered.
The judgement means Theresa May cannot begin talks with the EU until MPs and peers give their backing - although this is expected to happen in time for the government's 31 March deadline.
The government argues that ministers have the power - but opponents say they need Parliament's approval to start the two years of negotiations.
But the court ruled the Scottish Parliament and Welsh and Northern Ireland assemblies did not need a say.
If ministers lose the appeal, they will have to ask Parliament to vote on legislation that triggers Article 50.
Brexit Secretary David Davis will make a statement to MPs later on Tuesday.
The outcome of the Supreme Court case, heard by all 11 justices over four days in December, will not overturn the referendum result but determine which course towards leaving the EU is lawful.
During the Supreme Court hearing, campaigners argued that denying the UK Parliament a vote was undemocratic.
Prime Minister Theresa May has said she wants to invoke Article 50 - formally notifying the rest of the EU of the UK's decision to leave - by the end of March, setting in train negotiations over the terms of the UK's exit.
But the government said it already had the powers to trigger Article 50 of the Lisbon Treaty - getting talks under way - without the need for consulting MPs and peers.
Lord Neuberger, president of the Supreme Court, will read out a summary of the court's findings in a session expected to last five minutes. Members of the public are able to attend and will be allocated seats in the courtroom, as well as two adjacent rooms, on a first-come, first-serve basis from 09:00 GMT.
Reading out the ruling, Supreme Court President Lord Neuberger said: "By a majority of eight to three, the Supreme Court today rules that the Government cannot trigger Article 50 without an Act of Parliament authorising it to do so."
The full court ruling will then be published on the Supreme Court's website.
Outside the court, Attorney General Jeremy Wright said the government was "disappointed" but would "comply" and do "all that is necessary" to implement the court's judgement.
The case against the government was brought by investment manager Gina Miller and hairdresser Deir Tozetti Dos Santos.
Gina Miller, one of the campaigners who brought the case against the government, said Brexit was "the most divisive issue of a generation", but added that her victory was "not about politics, but process".
The points at stake
Labour leader Jeremy Corbyn said: "Labour respects the result of the referendum and the will of the British people and will not frustrate the process for invoking Article 50."
Read legal correspondent Clive Coleman's full analysis
Article 50 will begin exit talks with the EU, which are expected to last up to two years.
Lawyers for the government argued that ministers could trigger Brexit under the Royal Prerogative - executive powers to make and break treaties. They added that Parliament had passed legislation for the referendum knowing what it could lead to - and had not asked for the final say.
Liberal Democrat leader Tim Farron said he would press for a second referendum on the final deal reached between the UK government and the EU.
But lawyers for the government's opponents said ministers had no power to change the constitution of the UK because only an act of Parliament could take away the rights and laws created during four decades of EU membership.
The case against the government was brought by Ms Miller, an investment manager, and hairdresser Deir Tozetti Dos Santos.
The case also heard arguments from Scotland, Wales and Northern Ireland about whether the devolved bodies had a say.
The Supreme Court's judgement backs that given by the High Court last year, against which the government appealed.
Two lawyers representing Brexit opponents from Northern Ireland argued that the process unlawfully picked apart key parts of the Good Friday Agreement which gave the EU a special role in the political bodies that emerged in the peace process.
If the government loses its appeal, it is expected to swiftly publish legislation asking Parliament to trigger Article 50, with the aim of it being approved by MPs and peers by March. Brexit Secretary David Davis is expected to make a statement to the Commons to outline the government's next steps.
Ms Miller told the Guardian she hoped the government would come up with a "watertight" piece of legislation "to avoid loopholes that people can come back on", adding that she was not trying to frustrate Brexit and the issues at stake were legal not political.
There has been criticism by sections of the media after the High Court upheld Ms Miller's legal challenge, with the Daily Mail branding the judges "enemies of the people".
But Lord David Hope, who was deputy president of the Supreme Court for four years, said that idea was "a complete misconception".
"Our country relies on the rule of law and respect for the law is absolutely crucial," he told the BBC's Today programme.
While Labour leader Jeremy Corbyn has said his MPs will be told to approve the bill because of the referendum result, there is speculation that dozens of them may rebel.
On Sunday, Scotland's Brexit minister Mike Russell told BBC News there were no circumstances in which the SNP's 54 MPs would back triggering Article 50.
However, the government is still expected to win a Commons vote with nearly all 329 Conservative MPs backing the move.
In November, the High Court rejected the government's arguments regarding Article 50 but ministers opted to bring an appeal - saying they had a strong case and the Supreme Court hearing would also establish key points of constitutional law.
Attorney General Jeremy Wright led the government's legal team assisted by senior counsel James Eadie, while crossbench peer and constitutional historian Lord Pannick headed Ms Miller's legal representation.
