Why is there a row over the UK’s new EU commissioner and could Boris Johnson be punished?

It came a bit out of the blue: on Thursday the European Commission launched legal action against the UK over its failure to nominate a new EU commissioner. Here’s everything you need to know about it.

The European Commission is the EU’s executive branch, and it acts a bit like a cabinet government, coming up with new European legislation. It has 28 members (or “commissioners”), one appointed by each member state, though they are each bound to act in the interests of the union as a whole rather than their home country.

A new commission is supposed to take office on 1 December (led by president Ursula von der Leyen, who is replacing Jean-Claude Juncker). The UK is still a member state, so under the EU treaties it has to appoint a commissioner.

The initial reason was that the UK was absolutely, definitely, going to be leaving the EU on 31 October, and there was absolutely no chance of this not happening – so there would be no need for a new commissioner because the UK wouldn’t be a member on 1 December. You may recall that the UK did not in fact leave on this date, so one is now needed.

Except, now we’re in election season, and Boris Johnson has said he isn’t going to be appointing a commissioner, and he doesn’t really want to break another promise to Brexit voters, who he needs to stay in Downing Street.

So the UK’s response was to drag its feet for a few weeks and be extremely vague when asked about whether it was going to appoint a commissioner. Then the election campaign kicked in properly, and now the UK government is saying that it can’t by convention make international appointments during an election period.

The EU is having none of it and cites EU case law that says member states can’t use domestic law to ignore their obligations under EU treaties. The bloc has opened a so-called infringement procedure against the UK over the whole thing.

It also points out that the European Council decision that gave the UK a Brexit extension specifically said the UK has to appoint a commissioner and that the British government would abide by the principle of “sincere cooperation”.

The UK has until 22 November to give its response to the commission’s notice, and then the commission will issue something called a “reasoned opinion” on what happens next, taking into account all the evidence. It will ask the UK to comply, basically, within yet another time limit. If the UK does not comply within that time limit, then the case goes to the European Court of Justice (ECJ).

Frankly, by then the situation will probably have been resolved: either because we’ll have left the EU, or a new government will have just appointed a commissioner. But theoretically the ECJ can issue “financial penalties” against member states who refuse to comply with the law.

Frankly, probably not a lot. The EU treaties do say there should be 28 EU commissioners, but nobody in Brussels really believes the lack of a UK commissioner will block the commission from taking office. Commissions have been a member down on previous occasions for various unavoidable reasons, and the world didn’t end.

The UK’s commissioner would only be taking office for two months anyway, if Boris Johnson wins a majority at the general election and we leave the EU on 1 February – so it isn’t really a big deal.

There are different theories. One line of thinking is that Brussels is a stickler for the rules and likes to pointlessly make a big deal about violations with no regard to context.

But another idea doing the rounds is that the EU is trying to help out Boris Johnson, who it wants to win a majority and pass the Brexit deal it just struck with him.

Eurocrats here are perfectly aware that a nice fight with Brussels will help the prime minister win Brexit voters to his side and may have decided to give him one on a silver platter. Of course, we can’t know their motivation and that’s all speculation.