Government lawyers are exploring the possibility of arguing in the supreme court that the article 50 process could be reversed by parliament at any time before the UK completes its exit from the European Union.

Prominent academic experts have told the Guardian they know the government’s legal team has sounded out lawyers about the potential change of tack, which some argue would lead to a victory in the case brought by Gina Miller and other campaigners.

Prof Takis Tridimas, an expert in EU law at King’s College London, said: “I know that the issue of revocation is a live issue in terms of the supreme court hearing.” He had heard that the government had commissioned research on the subject, he said.

Earlier this month, the high court ruled that the government could only invoke article 50, which begins the EU exit process, through a parliamentary vote. The case was decided on the basis that, once article 50 was triggered it was irreversible and British citizens would inevitably lose rights granted through the 1972 European Communities Act.

Royal prerogative powers – the government’s executive authority – cannot be used to repeal rights granted by parliament, the three high court judges concluded in their ruling, which was sharply criticised by several tabloid newspapers, including the Daily Mail which described the judges as “Enemies of the People”.

If the government argued that MPs could vote to revoke article 50 during the exit negotiation period, some academics say, the outcome of the government’s appeal to the supreme court would be different, because it would imply that the sovereignty of parliament had not been removed.

Dr Eirik Bjorge, a senior law lecturer at Bristol University and an expert in EU law, said: “If the government decides to – and is allowed to – argue that the article 50 notice can be revoked, then it is all but sure to win in the supreme court. In those circumstances it cannot be said that, once the trigger has been pulled, the bullet will inexorably hit the target and expunge our rights under the European Communities Act 1972.”

Tridimas is one of those who believes the article 50 process could be reversed before the UK’s exit from the EU had been completed. “My view is that it is reversible,” he said. “There’s nothing in the wording of article 50 which says that it cannot be withdrawn. The Vienna convention on the law of treaties says that they can be reversed unless they state otherwise. The point of no return is two years after notification has been given [to the EU].”

Prof Paul Craig, an Oxford University expert on both EU and constitutional law, said the triggering of article 50 should be revocable by parliament. “It is a cardinal legal principle that a party is not bound by a contract or treaty until agreement has been reached,” he has argued in a blogpost. “The consequences of not being able to revoke would be particularly severe: withdrawal would have to proceed even if invocation of article 50 triggered an economic meltdown in the country.”

However, Craig said, enabling parliament to give its approval at an early stage might have dangerous consequences for democracy later on: “There is a deeper paradox in this litigation.”



He said the claimants, who he said would like Britain to remain in the EU, were “willing to risk everything for some parliamentary voice at the trigger stage”, but this could result in a decisive parliamentary vote to invoke article 50, which would be difficult to undo subsequently.

“The government wishes to exit the EU. It conceded the article 50 point knowing that it might then lose the immediate battle, and would therefore have to seek parliamentary approval, but was confident enough that this would be forthcoming, and that thereafter the war was won, since the triggering, once done, was irrevocable.”

The government has already submitted its initial grounds for appeal at the supreme court. The papers do not indicate any shift of emphasis so far in the way the case will be presented, although it is possible that could change before the hearing in December.

A government spokesman said: “Our position is clear: the country voted to leave the EU and we will respect the will of the British people. The government told the high court that as a matter of firm policy, once given, the article 50 notice would not be withdrawn. Because legal proceedings are under way it would not be appropriate to comment further.”