Calais has had a huge problem with refugee camps. As I understand, they’re obligated by the EU to control migration through the Chunnel into Britain. There would be no EU obligation if Britain leaves, is what this mayor is saying. He would prefer not to have the problem, himself.
I don’t believe that there was any formal solution in place for the Calais migrants.
Calais is just the place that the migrant problem can that has been kicked down down the road currently occupies.
All of the political representatives have been content to kick the can down the road and let it become someone else’s problem. In Calais that took the form of appeasement by the mayor. Now the mayor blames the British. However, I am not sure that the British have any obligation at this moment to the migrants. So the French might use a trade blockade as a bargaining chip, but trade goes both ways, and the French who depend on trade with the British would probably take offense to a trade blockade by France, so that does not sound very likely to me.
I think what is difficult for everyone to believe is that Brexit puts a roadblock into the notion of kicking the can down the road, and unfortunately for Calais, it is now the new end of the road. The only “progressive” way out is for the EU to threaten the UK with severe trade sanctions. However, that means that EU is forced to admit that it is not capable of handling its own problems, in particular, very visible problems that its kick-the-can policies played a big part in forming.
It is likely therefore that EU will have to come up with a plan to absorb the Calais migrants and furthermore come up with a plan to absorb the Calais migrants-to-come. They will also have to do this under public scrutiny of some sort. The only political analog I can think of is suddenly and unexpectedly being unable to increase the national debt limit. In other words, there will be all kinds of very unpleasant political repercussions. EU politicians, like markets, abhor uncertainty— they tend to want to keep themselves in power. A situation in which outcomes are uncertain provides plenty of political uncertainty for many of them. I suppose the EU political scene will shift to a blame game, with everyone scrambling to avoid being stuck with some share of the blame for the additional cost of handling the migrants, plus some NIMBY effects as well.
To some degree I think the migrants were counting on the EU to come up with a means by which they could cross the Channel legally. Now with Brexit, I think that scenario is at best a long shot, so the migrants will need to modify their world view to incorporate a Britain that they do not qualify to migrate to under any conditions (without adequate skills to qualify for legal immigration). After a while, there will be a mayor in Calais who reflects the new reality, and demands action from the French national government to help disperse the migrants and possibly even return them to wherever they came from.