Jean-Luc Moudenc, the mayor of Toulouse, has sent a formal warning to Francois Piquemal, an opposition councillor and La France Insoumise member of parliament, over how he conducts civil weddings at the Capitole. The letter runs to more than two pages and ends with a plain statement of consequence: if the failings it sets out are not corrected and the basic rules not strictly observed, Moudenc may withdraw Piquemal's ability to marry couples at all.

The dispute began last week when Nathalie Capdevielle, the councillor responsible for ceremonies, published a video accusing Piquemal of filming himself from the back of the Salle des Illustres, speaking loudly, while she was officiating. She called it a lack of respect and objected more broadly to what she described as a politicisation of weddings, pointing to Piquemal telling residents of Toulouse they could decline to be married by the radical right and ask for an LFI councillor instead. Piquemal called the incident minor and said it had been blown out of proportion.

The legal point in Moudenc's letter is the part that matters, and it is not obvious to most people. An opposition councillor can conduct a wedding, but doing so is not an entitlement. It is a customary courtesy extended when a couple asks for it, granted at the mayor's discretion, and the law does not require him to grant it. Moudenc writes that he has always allowed it. He is also making clear that what he has always allowed he can stop allowing.

That asymmetry is the whole story. A mayor holds the civil registrar function and delegates it. A councillor performing a marriage is exercising borrowed authority, and the borrowing can be ended. It means a disagreement that looks like a row about manners is in fact a disagreement in which one side controls the other side's access to a public duty, and that is worth stating plainly whichever party holds the office.

On the substance Moudenc invokes neutrality, writing that a wedding is neither the moment nor the place for political debate and that Piquemal respects neither the letter nor the spirit of the task entrusted to him. He also raises a second episode, a wedding on 25 June that Piquemal was due to conduct and did not attend without notifying anyone, which is a different order of complaint from a filmed video and harder to argue with.

Piquemal replied the same day with his own published letter calling on the mayor to see reason, and said by telephone that he does no more politics than anyone else, and none during ceremonies. Both letters were made public within hours, which tells you what kind of exchange this is. Toulouse goes to the polls again in this cycle, and a fight conducted through open letters about who is politicising a wedding is itself a campaign document.