Parliament has passed legislation requiring the premier to ask the other 27 EU leaders for an extension if no deal emerges from a Brussels summit on October 17-18.
But he is now facing a legal challenge to ensure he does not follow through on his threat to take Britain out of the bloc on October 31 come what may.
Johnson has repeatedly promised to both follow the law and take Britain out by the deadline — a contradictory position prompting speculation the government may have identified a loophole to end its EU membership.
Lawyer Jo Maugham, a key opponent to Brexit and claimant in the case, posted the documents on Twitter on Friday.
He said the government had submitted documents to Scotland’s highest civil court stating that Johnson “accepts that… he will send a letter (asking for an extension) by no later than 19 October 2019” if there is still no new deal.
UK media have speculated Johnson could still try to get Brexit done on time by sending a second letter alongside the request, stating he did not want the extension and was only following the law.
Others suggested he could ask one of the EU leaders to veto the extension, which requires unanimous support.
According to the documents submitted to the Court of Session in Edinburgh, Johnson says he accepts “he is subject to the public law principle that he cannot frustrate its purpose or the purpose of its provisions.
“Thus he cannot act so as to prevent the letter requesting the specific extension in the act from being sent,” the court document says.
Maugham said despite that, the court itself could still decide “to sign the letter for the prime minister” if Johnson still tried to stick to his promise to leave on October 31.
He and others behind the case also want the court to require Johnson to seek an extension to avoid leaving the EU without a deal.
A full hearing would be set for Tuesday if the judge decided to issue a formal ruling in the case, Maugham said.
