With respect Golden Paws, your information is incorrect. The French are are simply implementing the EU rules for non-European countries that have been in existence for many years and which the UK, when it was a member of the EU, helped to formulate and voted for.
You raise an interesting point regarding Northern Ireland. The same rules that concerns Striker must surely apply to any anglers going to Northern Ireland to fish. Although N Ireland is part of the United Kingdom it has remained in the single market and is obliged to conform to the single market rules. The same rules that the UK, as a member of the EU, helped to formulate and vote into existence.
All the UK has to do, to be able to export sausages from UK to N. Ireland, is agree to conform to the same quality standards for the preparation of sausages as the rest of the EU has done. For some reason this is politically unacceptable.
The alternative is to abandon this agreement and move the border from the Irish Sea to between North and South Ireland. This would infringe the Good Friday Agreement. If this were allowed to happen, the rest of the civilized World would certainly turn against the UK and the “troubles” would start all over again.