French fishing boats have been protesting outside the port of St Helier in Jersey, in a dispute over access to waters around the island.
France claims that unfair terms have been imposed, and it's threatening to cut off Jersey's electricity supplies in retaliation.
Why are French fishermen angry?
The French authorities say new rules governing access for foreign fishing boats to Jersey's territorial waters are unacceptable.
Under post-Brexit rules, which came into force this month, 41 licences or permits have been issued to French fishing vessels to operate in Jersey's waters.
Access has been granted based on how much fishing they did there between February 2017 and January 2020.
But while some French boats have provided comprehensive information about the amount of fishing they have done in the past, others haven't.
That means 17 of the 41 boats have been given much less access than they were expecting. If the owners produce more evidence, Jersey says, their licences can be amended to give them more.
But France says there was no consultation about other new conditions affecting all boats which, it says, "were not arranged or discussed, and which we were not notified about".
What are these conditions?
The Jersey government has added what it calls two "very minor" conservation measures to the new access agreement, dealing with dredging and nesting areas. It argues that neither of them are unreasonable.
France argues that the new rules create restricted zones, and limit the kind of fishing equipment which can be used.
They say many of their local boats could be put out of business, and smaller boats would also be affected.
If Jersey's position does not change, France is reserving the right to retaliate.
It's worth noting that the current dispute does not involve other Channel Islands, such as Guernsey.
What kind of action could France take?
France has threatened to cut electricity supplies to Jersey.
An estimated 95% of the island's electricity arrives by undersea cables from France, which is only 14 miles away.
This may be just tough talk, but France would theoretically be within their rights to take this action.
The Brexit deal says that in some cases, both the UK and the EU can respond to a breach of one part of the agreement - eg in fishing - by imposing sanctions in another area (electricity supplies).
But they would have to prove that the agreement really had been breached, and that would take some time.
Jersey's status is complicated because it is not part of the UK, and it was never part of the European Union.
It is what's known as a Crown dependency, which means it has substantial freedom from Westminster, and exercises day-to-day control over its fishing waters.
However, the UK government is ultimately responsible for its international relationships. That's why access to fishing waters around the Channel Islands are dealt with specifically in the new UK-EU trade agreement.
What's the EU's position?
The European Commission backs France and says the terms of the trade deal are not being respected.
The UK says it informed the European Commission about the new licences - but the Commission says this happened only one day before they came into effect, giving no time for any discussion.
Many of these technical issues could well be resolved by holding further talks. But negotiations on fishing are always rather fraught.
Does this reflect wider disputes?
The row about access to Jersey waters comes at a sensitive time.
More general negotiations are taking place between UK and EU officials about the division of quotas this year for shared fishing stocks.
And there have been other protests. Last month French fishermen blocked the French port of Boulogne to try to prevent imports of fish caught by British boats.
They were complaining about restricted access to fishing in waters between six and 12 nautical miles from the British coastline, and seeking guarantees that they would be able to unload their catch at British ports.