Ministers are “not legally compelled” to give Holyrood and the other devolved administrations a vote on the triggering of Article 50, the highest court in the UK has unanimously decreed.
Although Scottish First Minister Nicola Sturgeon has pledged to give MSPs a vote on the issue, this will now only be a symbolic ballot.
Tory MSP and law professor Adam Tomkins said the Supreme Court decision was a “comprehensive defeat” for the Scottish Government.
As the ruling was announced, Professor Tomkins tweeted: ” Both Governments lose: UK needs legislation to trigger Art 50 but this is a UK matter for the UK, not a matter that triggers Sewel.”
He added: “UK Supreme Court unanimous that this is not a devolved matter. Comprehensive defeat for the Scottish Government.”
Announcing the decision on the devolution issues, Supreme Court President Lord Neuberger said: “The court unanimously rules that UK ministers are not legally compelled to consult the devolved legislatures before triggering Article 50.
“The devolution statutes were enacted on the assumption that the UK would be a member of the EU, but they do not require it. Relations with the EU are a matter for the UK Government.
“The Sewel Convention plays an important role in the operation of the UK constitution but the policing of its scope and operation is not a matter for the courts.”
Downing Street insisted the Supreme Court judgement – which upheld a previous ruling that MPs must be given a vote on the triggering of Article 50 to start the the formal process of leaving the European Union – would not affect its timetable for this.
A spokesman said: “‘The British people voted to leave the EU and the Government will deliver on their verdict – triggering Article 50, as planned, by the end of March. Today’s ruling does nothing to change that.”
SNP MPs have pledged to lodge 50 amendments to the legislation that will now have to be brought forward at Westminster.
The SNP also insists the UK Government must seek the unanimous agreement of the Joint Ministerial Committee (JMC) – which brings together the UK Government and the devolved assemblies in Belfast, Cardiff and Edinburgh – that the “triggering of Article 50 encompasses the devolved administrations of Scotland, Wales and Northern Ireland”.
Alex Salmond, SNP international affairs spokesman at Westminster, said he hoped the Supreme Court verdict “brings this Tory government back to the reality that they cannot simply bypass elected Parliamentarians to fulfil their role in carrying out due and proper scrutiny of one of the biggest decisions facing the UK”.
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.
“For over six months the concerns surrounding a hard Tory Brexit have been echoing throughout the land and yet the Prime Minister has not listened.
“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.
“Now is the time to sit with the Joint Ministerial Committee and not just casually acknowledge, but constructively engage. Consultation must mean consultation.
“Our amendments will address the very serious concerns facing the UK and the very real issues that the UK Government has, thus far, avoided.”
Although SNP MPs will seek to amend the Article 50 legislation, they are still expected to vote against it in the House of Commons.