A LANDMARK legal opinion that MPs can halt Brexit offers “a roadmap out of the shambles”, according to the Scottish politicians who fought for a year to obtain it.

READ MORE: ECJ Advocate General says UK can revoke Article 50 unilaterally 

The Advocate General to the European Court of Justice (ECJ) said this morning that the UK is able to cancel Brexit unilaterally, without the consent of the other 27 EU countries.

Advocate General Manuel Campos Sánchez-Bordona said MPs had the power to revoke the Article 50 withdrawal process any time before it ends next March.

He categorically rejected the UK Government’s argument that the issue of revocability was “academic and hypothetical”, and its call for the case to be dismissed.

Instead, he said the dispute was genuine, of obvious practical importance, and answering it was “essential” to clarify the matter.

He said the Article 50 process should be handled like any other international treaty, with parties allowed to withdraw unilaterally if they changed their mind, not trapped inside.

His opinion is not binding on the court, but is highly influential, and is likely to be mirrored in the full ECJ judgment in a few weeks’ time.

It is a significant boost for those seeking a People’s Vote and a blow to Theresa May, as it undermines her argument that Brexit is a straight choice between her deal and No Deal.

The Scottish Government paid tribute to the “perseverance” of those behind the case.

READ MORE: Joanna Cherry: Why we must know if MPs have the power to revoke Article 50 

The opinion was the result of a year-long fight by Scottish politicians who wanted the ECJ to give a definitive ruling on whether MPs could order the UK government to stop Brexit.

Led by Green MSP Andy Wightman, the group included Labour MEPs Catherine Stihler and David Martin, SNP MEP Alyn Smith, SNP MP Joanna Cherry QC, LibDem MP Christine Jardine, and was supported by Jolyon Maugham QC of the Good Law Project.

After an early defeat at the Court of Session, they won an appeal heard by Scotland’s top judge, then fended off last-ditch UK Government attempts to stop the case reaching the ECJ.

A panel of 27 European justices finally heard the case last month.

Mr Smith said: "This is a huge win for us, and a huge step forward from the highest court in the business, and confirms what we have been hoping for: that the UK can indeed change its mind on Brexit and revoke Article 50, unilaterally.

“The Advocate General Opinion is not the final judgment, but the practice of the ECJ is that the judges tend to follow the Opinion, so this is a major landmark.

"We now have a roadmap out of the Brexit shambles, a bright light has switched on above an 'Exit' sign and the false choice being offered to MPs at Westminster - that it is Mrs May's disastrous deal or chaos - is shown for what it is, an abuse of Parliament.

"There are other options, and we can stop the clock."

Once the ECJ delivers its verdict, it will be for the Court of Session, which referred the matter to the Luxembourg court, to act next.

Mr Wightman said: “This is a very welcome opinion that vindicates the argument we made to the Court of Justice on 27 November. We await the Court's ruling in due course followed by the final decision of the Court of Session.

"It is now highly likely that, if the people of the UK were to change their minds and decide to remain in the EU, there is now a route to doing so. This would involve the extension of the Article 50 notification period and a second referendum.

"This is the only option that ends the current chaos and provides a considered and sincere means by which the citizens of the UK can have the final say in this process."

The Herald:

Ms Stihler added: “"This is a landmark opinion from the Advocate General.

"He has made clear that the UK can stop the ticking clock of Brexit before it is too late.

"If judges accept his opinion, the UK will have the option of halting the process, and will be able to offer the chance to keep the best deal we have as a member of the EU through a People's Vote - rather than choosing between Theresa May's bad deal or a catastrophic no-deal scenario."

A massive vindication for myself @andywightman @AlynSmith @Ross_Greer @C_Stihler_MEP @davidmartinmep & @JolyonMaugham & our fantastic legal team. We are optimistic the full court will follow this ruling #Art50 #StopBrexit #PeoplesVote https://t.co/RRTDoyRHh6

Lord Kerr, who helped draw up Article 50, and has long argued it was revocable, said: “This is no surprise and, if the court agrees, will confirm that it is still up to us to decide whether we want to keep the existing deal we've got in the EU rather than leave on the Government's terms.

"The choice facing us is not simply between the Government's deal and no deal. We can choose to change course. There is still time and, until the UK has left the EU, the Article 50 letter can be withdrawn.

"Despite some of the bogus claims that have been made by those who oppose staying in the EU, there would be no price to pay - political or financial - if we were to take back the Article 50 letter.

"With support growing across the country for a People's Vote, it is clear to me that this is the best way forward. The people should have the right to choose."

SNP Constitutional Relations Secretary Michael Russell said: “I welcome the Advocate General's opinion and look forward to the final judgment of the Court of Justice.

"Rejecting a bad deal must not mean leaving with no deal.

"It is a tribute to the perseverance of the Scottish parliamentarians involved that we will finally get clarity from the Court of Justice on this important question."

On Twitter, Ms Cherry said the opinion was a "massive vindication" for those who brought the case, adding: "We are optimistic the full court will follow this ruling."

Mr Maugham added: "It's a very important moment, it makes the path to remain much easier.

"We know that if the Advocate General's opinion is followed we will know that we can keep all of the options and the special privileges that we enjoy as a member of the EU. It puts the decision about whether to remain into the hands of MPs, which is where it should be."

Former Tory attorney general Dominic Grieve said the opinion was “clearly significant”.

He said: “It is certainly helpful [getting a People’s Vote] because it removes one of the arguments, which is: 'Oh well, they would never allow us to change our minds.'"