This is how 'The Local.fr' are reporting it. It is industrial action, though not a strike.
The reason behind the industrial action, which began on March 4th, is customs officials are trying to press demands for higher pay and demonstrate what will happen if greater controls are put in place once Britain leaves the European Union, planned for later this month.
Instead of going on strike meaning they would not work at all the customs officers have been carrying out work-to-rule industrial action which means that they only do what is required by the rules of their contract.
This means that they precisely follow all safety or other regulations, which has means lots of checks and questions which has slowed down the flow of passengers through terminals at Eurostar, EUrotunnel and the ports in Calais and now at airports in the Alps.
Vincent Thomazo from UNSA union told The Local last week that customs' agents wanted to get the message across to the French government that they were simply not ready for Brexit.
"Our aim is to attract attention to our worsening conditions of work which will only get worse once Brexit happens," Thomazo said.
I think in all of this we are forgetting that the decisions made in the UK, for whatever reasons, do have an impact further afield. There are (more than) two sides to this divorce, the decision to vote leave has further ramifications than we could have ever really known. .......No man is an island.