C RITICS OF Theresa May often attack the prime minister for invoking Article 50, beginning the Brexit process, before her government had decided the form of exit it wanted. Setting a two-year deadline that expires on March 29th weakened her negotiating position. Yet there was a reason for the timetable, besides her own haste. It meant that Britain would be out of the EU before the next elections to the European Parliament, which are due between May 23rd and May 26th. Talk of extending the Article 50 deadline, which has grown louder after Parliament’s emphatic rejection of Mrs May’s Brexit deal this week, threatens to complicate these elections—and not just in Britain.

The plan was (and is) that, since Britain is leaving the EU , it should not elect new MEP s. The European Parliament has already reallocated 27 of the 73 British seats to other EU countries, keeping the rest in reserve for any future expansion of the club. If Article 50 were extended for a couple of months, that might not present a problem. But if the extension meant that Britain was still an EU member in late May, questions would be raised about Britain’s MEP s.

Some suggest that today’s British member S could stay in their posts or be replaced by nominees from Westminster, to avoid holding elections. That might work at least until the new European Parliament formally meets on July 2nd. But it is hard to see a stopgap going beyond then. Any Briton could challenge their loss of voting representation. And the European Court of Justice would surely rule that, as Britain was still formally a member, it must elect MEP s.

Britain’s Electoral Commission is ready for this and even has a budget in place to hold such elections. Yet it would seem farcical to do so if Britain were on its way out. As Agata Gostynska-Jakubowska of the Centre for European Reform, a think-tank, notes, it would also stop the reallocation of the 27 British seats, screwing up other countries’ polls.

An Article 50 extension would raise another complication. To take effect, any withdrawal treaty must be ratified by the European Parliament. Today’s MEP s say they would approve Mrs May’s deal. But their final plenary session will be in mid-April. In theory, MEP s could be summoned to an extraordinary session before the new parliament meets in July. But that would be unpopular, especially if it clashed with the elections in May.

The alternative of asking new MEP s to ratify a Brexit deal would be awkward. Committees would not have been formed and the existing Brexit steering group would be shut down. If an eventual deal were made significantly different from the current one—for instance, by revising the terms of the Irish backstop—new MEP s could be tempted to reject it.