AN eagerly awaited legal opinion on whether Westminster can halt Brexit will be delivered at Europe’s top court today following a year-long battle by a group of Scottish politicians.

UPDATE: ECJ Advocate General says UK can revoke Article 50 unilaterally 

Campos Sánchez-Bordona, the Advocate General of of the European Court of Justice, will give his view on whether MPs can revoke the Article 50 withdrawal process unilaterally.

The ruling is preliminary, not binding, but is expected to be followed by the 27 judges who considered the issue last month when they deliver their final verdict in a few weeks.

If the Advocate General rules MPs can order the UK government to revoke Article 50 it would make Theresa May’s battle to have her Brexit deal approved by MPs even harder.

Halting Brexit would be another option before MPs at the December 11 meaningful vote besides Mrs May’s deal and No Deal.

The case was referred to the ECJ by the Court of Session, as a result of a legal action led by Green MSP Andy Wightman.

SNP MP Joanna Cherry QC, Labour MEPs Catherine Stihler and David Martin, SNP MEP Alyn Smith, LibDem MP Christine Jardine and Green MSP Ross Greer were also part of the action, which was supported by Jolyon Maugham QC of the Good Law Project.

Because Article 50 is silent on whether it can be revoked unilaterally, the politicians asked the Court of Session to refer the matter to the ECJ for a definitive ruling.

The action was resisted throughout by the UK government who argued the issue was hypothetical and academic, winning an early victory in the summer.

However Scotland’s most senior judge, the Lord President Lord Carloway, and two other judges later overturned that ruling on appeal, and said the issue was far from academic.

Lord Carloway also rejected a bid by the UK Government to stall the case by referring it to the UK Supreme Court on appeal.

When the UK Government then tried to appeal directly to the UK Supreme Court, ministers were rebuffed again, with justices saying the ECJ ought to give its view first.

After receiving written submissions from both sides, the ECJ held a four-hour hearing on November 27 to consider oral arguments.

The UK Government said it didn’t have a view on whether Article 50 could be revoked, and instead argued the case out to be thrown out as inadmissible.

It was being used as “ammunition” by opponents of Brexit, Lord Keen, the Advocate General for Scotland, told the judges.

Lawyers for the EU Council and European Commission argued Article 50 could be revoked, but said it would require unanimous agreement from the other 27 EU states.

Commission lawyers said that a unilateral power could potentially result in states abusing the system, pretending to leave as a gambit to get a better deal for themselves.

The chief lawyer for the EU Council said a unilateral withdrawal mechanism could lead to “disaster”, of which “the main victim could be the European project altogether”.

It is possible therefore today’s ruling will say Article 50 can be revoked, but not unilaterally.

Mr Greer said MPs should be able to vote on Mrs May’s deal knowing “all the options available to them”.

He said: “We know that deal is an option. We know No Deal is an option. But as the Prime Minister said herself, No Brexit is also an option, and MPs deserve legal clarity on that.

“They deserve to know if Article 50 can be revoked by the unanimous agreement of all 27 other European states. They deserve to know if it can be unilaterally revoked by the UK parliament instructing the government to do so. We believe they should have that option.”

Mr Smith said he hoped “a bright new Exit sign” would appear next to Mrs May deal and No Deal when the opinion comes this morning.