Photo: Han Yan/Xinhua News Agency/PA Images

Boris Johnson says that his top priority in government is to take the UK out of the EU by 31^st October. It sometimes feels like that is really his second priority. His top priority is to entertain constitutional lawyers.

On Saturday night, the British government sent three letters to the EU. The first, which was required by the “Benn Act” passed by parliament earlier this year, was a request for an extension of the Article 50 period until the end of January 2020. The second was a covering note from Britain’s man in Brussels, reminding the EU that the extension request was required by parliament. The third and final letter was the only one signed by Johnson himself: a meandering discussion of the political context for the letter, and a statement of the government’s policy.

Of the two pages of fluff that comprise that final letter, it is really one sentence that matters. “While it is open to the European Council to accede to the request mandated by parliament or to offer an alternative extension period, I have made clear since becoming prime minister, and made clear to parliament again today, my view, and the government’s position, that a further extension would damage the interests of the UK and our EU partners, and the relationship between us.” Was that unlawful?

The case against the prime minister goes as follows. It is trite law that a minister may not act so as to frustrate the purpose of a statute. As Lord Reid put it in the classic 1968 Padfield case, if a minister “so uses his discretion as to thwart or run counter to the policy and objects of the Act, then our law would be very defective if persons aggrieved were not entitled to the protection of the Court.” The purpose of parliament’s instruction that the prime minister send a letter requesting an extension was, obviously, to obtain an extension. In case there were any doubt about that, parliament specified the purpose itself: the prime minister, it said, “must seek to obtain an extension.” The offending sentence in the extra letter, the argument goes, did not seek to obtain an extension. Rather it sought to avoid one by encouraging the EU to refuse the request.

What might the prime minister say in his defence? He cannot argue that it was lawful for him to frustrate parliament’s purpose. That is too obviously wrong. But he might argue that he did no such thing. The prime minister merely noted that he has stated his view about getting Brexit done time and again. Indeed he has. It cannot be unlawful for the prime minister to say that he said what he said. It is not as if he was telling EU leaders anything they did not already know, nor telling them how to respond, nor attempting to take back the request. In any event, the Benn Act says that if parliament passes his deal before the end of October, he is allowed to withdraw the extension request. That still might happen. It is therefore possible that, on 31^st October, the UK leaves the EU and there is no extension request in Donald Tusk’s in-tray. It surely cannot be unlawful for the prime minister to contemplate that possibility.

Perhaps the two arguments will be exhaustively tested in court, judgment will be given, the judgment appealed, and the arguments rehearsed again in the Supreme Court. For my part, I desperately hope that this does not happen. None of it matters: the prime minister sent the request, the EU confirmed receipt, and EU leaders will decide how to respond on the basis of their own interests, not the wishes of a British prime minister who has in any case lost control and is taking orders from backbench MPs. A court battle would only encourage the prime minister’s opponents to do his election campaigning for him, by accusing him of doing everything he can—even beyond what the law allows—to make Brexit happen on 31^st October.

We could spend days arguing about whether the extra letter, on careful reading, was an attempt to get EU leaders to say no. But if it was, then those parts were unlawful and so null and void anyway: written in invisible ink in the eyes of the law. So, if the Court of Session in Scotland is asked to make a ruling on this tomorrow, I suggest it keeps things simple. “The prime minister had to seek an extension,” it should say, “and he did seek one. He sent the letter mandated by parliament. Under the UK’s constitutional requirements, the prime minister had no power to seek to avoid an extension and, as a matter of law, he cannot have done so—in that letter or any other.” That would make double sure that the EU ignores the extra letter—and would allow the rest of us to ignore it, too.