Do the Kermits seriously imagine that their noisy bluster over the squalid Calais migrants camp bothers us? Sure, they're piqued that their nation and economy is down the can, that in future they'll depend on German hand-outs to pay their public servants, that across the Channel our economy, free of the EU, will surge ahead to become Europe's wealthiest. Hence the threats and bluster to move immigration checks to UK territory.
Any such move will only further damage French trade. UK exports will get a rapid ride into France going outwards, but French imports will face long delays and freight queues stretching from Calais to Rouen. For we will be forced to two varieties of new border controls; on the entry ramps of UK registered P&O ferries in Calais, and on the exit ramps of DFDS ferries in Dover. Migrants and illegals will either be left in Calais or on board the French ships.
Dover turnaround times for the French ships will quadruple, as will their port fees. Likewise for UK ships in Calais. Fares will rise. Passengers and freight will seek other ports - killing jobs and income in Calais, which depends completely upon the port for its wealth.
It's really up to the Kermits; honour the existing treaty, or face severe restrictions on their exports to the UK from Calais and become the laughing stock of Europe with the MS Côte des Flandres and her sisters full of Ethiopians who won't disembark being fed and catered by DFDS, and with the key town of the Côte d'Opal becoming a depressed, run-down slum with rusting docks and empty warehouses.