BREXIT could be halted at the 11th hour after a landmark legal victory by a group of Scottish politicians who have taken on the UK Government. 

The cross-party alliance was yesterday granted permission to ask Europe’s highest court for an authoritative ruling on whether Brexit can he halted by MPs.

Scotland’s most senior judge said the question, previously dismissed by government lawyers as “hypothetical and academic”, should be referred as a matter of urgency to the European Court of Justice (ECJ) before Westminster votes on the final Brexit deal.

If the ECJ rules that Parliament can revoke the Article 50 withdrawal process without the permission of the other 27 EU states, it could, in theory, result in MPs stopping Brexit.

In practice, parliamentarians would be reluctant to overturn the result of the EU referendum. 

However, having the option available would reduce the chance of a chaotic no-deal Brexit if talks between the UK and EU were to collapse. 

That in turn would undermine the UK negotiating position in Brussels.

Theresa May was told by EU leaders on Thursday that her Chequers Plan for a soft Brexit “will not work” because its cherry-picking approach risks undermining the single market.

The snub humiliated and wounded the Prime Minister ahead of next week’s Tory conference.

In the words of EU Council President Donald Tusk, it also turned the next EU summit in mid-October into a “moment of truth” for Brexit.

Speaking in Downing Street yesterday, Mrs May demanded ideas, details and “respect” from the EU in order to break the impasse over trade relations and the Irish border. 

Her warning that the EU’s two current proposals both represented a bad deal, and that no deal remained better than a bad deal, led to an 
immediate drop in the value of the pound.

Mr Tusk said in reply he was a “true admirer of PM May”, but also that the UK was warned about “every detail” of the EU’s objections to Chequers weeks ago.

The legal battle was led by Green MSP Andy Wightman, alongside his fellow Green MSP Ross Greer, Labour MEPs Catherine Stihler and David Martin, and SNP MEP Alyn Smith.

The SNP MP Joanna Cherry, QC, and Scottish LibDem MP Christine Jardine were also involved.

They asked the Court of Session for a reference to the ECJ on whether parliamentarians could instruct the UK Government to withdraw the Article 50 notification underlying Brexit.

Their case was initially dismissed, but they won an appeal heard by the Lord President Lord Carloway, Lord Menzies and Lord Drummond Young. 

It is understood the UK Government could appeal the decision to the UK Supreme Court, however no decision has yet been taken.

A Government spokesman said: “We are disappointed by the decision of the court. We are giving it careful consideration. But as the Government has repeatedly said, we are committed to implementing the result of the referendum and will not be revoking Article 50.”

Earlier this year, lawyers acting for the Government claimed the politicians’ petition did not reflect political reality on the ground.

In June, Lord Boyd agreed, saying revoking Article 50 was not “a live practical question” and the group’s petition was “a clear and dangerous encroachment on the sovereignty of Parliament”, as it was up to Parliament to decide if it wanted an ECJ ruling.

However in a written appeal judgment, Lord Carloway said the question of revocation was “neither academic not premature” as matters had moved on, and asking the ECJ for a preliminary ruling was “necessary”.

He wrote: “It is clear in terms of the EU (Withdrawal) Act 2018, that MPs will be required to vote on whether to ratify any agreement between the UK Government and EU council.

“If no other proposal is proffered, a vote against ratification will result in the UK’s departure from the EU on March 29, 2019, a date which is looming up. It seems neither academic nor premature to ask whether it is legally competent to revoke the notification and thus to remain in the EU.

“The answer will have the effect of clarifying the options open to MPs 
in the lead up to what is now an inevitable vote.”

Lord Carloway included a draft text of the reference to the ECJ which asked the court whether EU law permits an Article 50 notice “to be revoked unilaterally” by an EU member state after it has notified its withdrawal and, if so, subject to what conditions and with what effect relative to the Member State remaining within the EU. 

It also requested an “expedited procedure” in “light of the urgency of the urgency of the issue in terms of parliamentary consideration and voting in advance of 29 March 2019”.

Concurring, Lord Drummond Young said that if MPs were to vote responsibly, “it is surely obvious that they should be properly advised as to the existing legal position... 

“In these circumstances it cannot be said in my opinion that the question of revocation of the Article 50 notification is merely academic or hypothetical.”

In his opinion, Lord Menzies said he was “in complete agreement” with the Lord President’s conclusions, reasoning and solution.

Good Law Project director Jolyon Maugham QC, who helped bring the case, said the ruling showed it was “not too late to wake up from the nightmare that is this government’s Brexit”.  

Mr Greer said: “This is about ensuring MPs are fully informed of their options at this time of national crisis. If negotiations collapse, as appears to be happening, we have to know that a No-Deal disaster is not the only option on the table.”

Ms Cherry said: “It’s vital for MPs to know whether Article 50 is unilaterally revocable before they are asked to ratify any agreement between the UK and the EU Council. 

“Given Theresa May’s humiliation in Salzburg the answer to this question is particularly important.”

LibDem MP Tom Brake and Labour MP Chris Leslie were also part of the legal action.

Mr Brake said: “The European Court now has the opportunity to confirm that the UK can unilaterally withdraw the Article 50 notice, something the government has constantly refused to admit.  

“This would establish the UK’s options to decide its approach to Brexit, democratically and positively, and underline that the choice for the UK is wider than just a revised version of Chequers or ‘no deal’. This will be critical for Parliament over the next three months.”

Mr Leslie added: “It’s clear that Parliament is going to have to step in and take over this process from Theresa May. If we’re to do this and put the country first, we need MPs to realise that is not irreversible now. We cannot afford to be artificially constrained by the narrow view of a few Government Ministers with their own agenda any longer.”