Nobody really knows if the UK could go back on Brexit even if it wanted to, experts say.
A panel of Europe specialists addressed the House of Lords Brexit committee this week and were quizzed on whether Article 50 could be revoked.
Catherine Barnard, professor of European Union and employment law at Cambridge University, said there had been disagreement between MPs and members of the Lords on whether the Brexit process could be reversed.
She told the committee: “On the question of revocability, there is still the very difficult question of whether it is a unilateral decision.
“Can we decide to revoke the notification, or do we also need to have the EU say ‘Yes, we welcome you back with open arms’; and the answer to that is it’s not clear.
“You can run arguments both ways, but the reality is only the [European] Court of Justice has got the jurisdiction to say that, and of course that raises further issues.”
Roderick Abbott, a senior adviser on trade policy at the European Centre for International Political Economy thinktank, said even if the UK decided it wanted to remain part of the union, the EU may take a different view and oppose its bid.
Barnard, who had previously warned UK businesses would be in for a “rude awakening” over fees they may have to pay to recruit foreign workers post-Brexit - said she did not believe the UK would crash out of the EU without a transitional deal and that one would be made “at the eleventh hour”.
Theresa May will address EU leaders in Brussels on Thursday evening in a bid to push ahead with “deadlocked” talks over what happens when Britain quits the bloc at the EU Summit.