The Supreme Court has ruled Theresa May must get approval from the UK Parliament to start the formal process of leaving the European Union.
Judges decided by a majority of eight to three that the prime minister could not use prerogative powers to trigger Article 50.
But they concluded unanimously Holyrood and the other devolved legislatures did not need a say.
Although widely anticipated, the outcome is a blow to Mrs May and puts pressure on her end of March deadline.
This would have been significantly greater had the court decided in favour of consulting the governments of Scotland, Wales and Northern Ireland, however.
Brexit bill to trigger Article 50 ‘will be straightforward’
And Brexit Secretary David Davis insisted yesterday that the existing timetable still stands.
He said legislation would be laid before the Commons “within days” and “in good time” for debate.
Making a statement in the House, the Tory frontbencher added: “This will be a straightforward bill.
“It’s not about whether the UK should leave the European Union, that decision has already been made.
“The point of no return was passed on June 23 last year. People want and expect us to get on with implementing the decision that was made.”
Once Article 50 is triggered, the clock starts ticking on the two-year period assigned to negotiate the terms of the UK’s withdrawal from and future relationship with the EU.
Extra time can be allocated, but only with the agreement of all 27 remaining states.
Labour Leader Jeremy Corbyn said his party would not frustrate the process of leaving the EU, but indicated it would seek to amend the forthcoming bill to prevent the Tories “using Brexit to turn Britain into a bargain basement tax haven off the coast of Europe”.
Meanwhile, the SNP confirmed it would table 50 “serious and substantive” amendments to the legislation.
These will include a call for the publication of a white paper and an agreement with the European Commission that any failure of the Westminster Parliament to ratify the final terms of negotiation would result in a revision of the current terms of UK membership.
UK parliament to vote on bill to trigger Article 50
Gordon MP and international affairs spokesman Alex Salmond welcomed the ruling which he said he hoped would bring the Tory administration “back to the reality” that they cannot bypass parliamentarians.
But the former first minister added: “The prime minister and her hard Brexit brigade must treat devolved administrations as equal partners – as indeed she promised to do.
“If Theresa May is intent on being true to her word that Scotland and the other devolved administrations are equal partners in this process, then now is the time to show it.”
Tim Farron, leader of the Liberal Democrats, said his party would not vote for Article 50 without a referendum on the final deal.
Mrs May has said MPs will get a vote on this, but has ruled out going back to the people a second time.
The High Court had already concluded the UK Government must seek MPs’ consent to activate the process of taking Britain out of the EU.
Ministers then appealed the verdict, prompting the hearing at the Supreme Court, during which lawyers for the Scottish Government had the opportunity to put their case.
Ruling on the role of the devolved legislatures, the Supreme Court judgement described the Sewel Convention – which states the UK Parliament may not legislate for devolved matters without the consent of the devolved legislature affected – as a “political constraint”.
But it added: “The policing of its scope and operation is not within the constitutional remit of the courts.
“The devolved legislatures do not have a veto on the UK’s decision to withdraw from the EU.”
Although MPs are expected to vote the Article 50 bill through, the ruling adds further uncertainty to the Brexit process and the pound fell yesterday following the news.