Some Mayor has said they want to renegotiate, which is a lot different to being told that immigration checks have to move to the UK side of the channel.
For a country that has opted to join the Schengen area the very very least such a country can do, if it has any decency, is to allow the checks on the masses they have willingly allowed to stream across their country in the hope of invading another to occur their side.
If I recall correctly this Calais mayor has tried to be a pain in the past too. I think that maybe he just likes to spout off for the publicity and local approval ?