Hmmm have they had their lawyers on this. Because if I was in government in Eire I wd be asking our border control to start setting up roadblocks on the Northern border to start checking lorries.
And there wd be uproar on both sides and it wd be very destabilizing but assuming the same racists live in Ireland as here plenty of popular support for stopping migrants.
And the Brits CD say BUT the NI Protocol says no hard border on the island and the Irish wd say aye but that's about goods and we're not checking the goods just for migrants.
And if you want to check if that's a lawful interpretation of the NI Protocol you'll have to exhaust domestic remedies and get a ruling from the Irish Supreme Court which will probably find this is a proportionate response to unchecked migration from the North as otherwise we cannot return these migrants to the UK. And then you'll have to appeal that to the European Court of Justice which was the thing you promised Brexit wd mean wd never happen and it wd be over your own fucking stupid immigration policy. So good luck with that.