The European Court of Justice will decide if the UK can reverse Brexit alone next week, a day before MPs vote on Prime Minister Theresa May’s deal.
The ruling, on a case brought by Scottish politicians, is being pushed through at breakneck speed in time for Tuesday’s vote.
Earlier this week a top adviser to the court said that Britain could stop Brexit without approval from other member states. These opinions are not binding on the judges, but are usually followed.
“Advocate General [Manuel] Campos Sanchez-Bordona proposes that the Court of Justice should declare that Article 50 [...] allows the unilateral revocation of the notification of the intention to withdraw from the EU,” the ECJ said on Tuesday.
“That possibility continues to exist until such time as the withdrawal agreement is formally concluded,” it said, giving the UK until 29 March to make up its mind.
The statement was seen as a victory for anti-Brexit campaigners and supporters of a second referendum.
“That puts the decision about our future back into the hands of our own elected representatives,” said Jo Maugham, a lawyer on the case.
MPs are widely expected to vote down the Prime Minister’s Brexit deal as it comes to the floor of the Commons next Tuesday.
Both Theresa May and the EU have stressed that this risks a no-deal Brexit which they say will be damaging for Britain.
“Every effort is being made on both sides of the Channel to stop Brexit," Nigel Farage said after the EU court's statement on Tuesday.