The AG proposed that the court should agree that article 50 allows for unilateral revocation within the two-year period from the notification of the intention to leave (that took place on March 29, 2017) and that this possibility remains until such a time as the withdrawal agreement is formally concluded and as long as the revocation is decided upon in accordance with the UK's constitutional requirements and is formally notified to the European Council.
Two attempts by the United Kingdom government to appeal against the referral to the European court were rejected, and the case was opposed by the government and the EU institutions in a hearing before all 27 ECJ judges last week.
Scottish MPs and MEPs had brought the case on Article 50 - a 250-word clause inserted into the EU charter eight years ago, which had never been used until the United Kingdom voted to exit the European Union in the summer of 2016. While it is a non-binding ruling, the opinion of Advocate Generals are mostly followed by judges at the ECJ. The possibility that the United Kingdom can go back on its decision will be alarming to Brexit hardliners and could encourage them to grudgingly support May's much-maligned roadmap for how the country should quit the bloc.
Opposition Labour finance spokesman John McDonnell said last week a second Brexit referendum "might be an option we seize upon".
But unanimous revocation could "in practice entail the forced exit from the European Union of a state which. continues to be an European Union member state in all respects", the advocate general said.
She said: "He has made clear that the United Kingdom can stop the ticking clock of Brexit before it is too late".
He said parliament was not necessarily facing a choice between accepting Mrs May's deal or leaving the European Union with no deal, and that "there are other options, and we can stop the clock". "There is now light at the end of the tunnel".
Who has brought the case?
Although the Advocate General's opinion is non-binding, the ECJ follow his opinions in the majority of cases.
"It puts the decision about whether to remain into the hands of MPs, which is where it should be".
Advocate General for Scotland Lord Keen QC, representing the UK Government, said the case is a "hypothetical validity challenge" and those behind it seek "political ammunition to be used in, and to pressure, the UK Parliament".
Asked if it made it more likely there would be a new public vote, he said: "It is certainly helpful because it removes one of the arguments, which is: 'Oh well, they would never allow us to change our minds'".
Clearly not trusting the rest of the European Union to agree with Britain if Parliament voted to reverse Brexit, the group petitioned the ECJ for the unilateral right to declare the United Kingdom under the continuing control of the exact same European Union that could not be counted upon to serve their interests in the first place.
"This is the only option that ends the current chaos and provides a considered and honest means by which the citizens of the United Kingdom can have the final say in this process".