[Skybird]

The RoI is limited in its sovereignty by EU laws and treaties, much like other member states as well. The RoI cannot even negotiate certain kinds of treaties by itsself anymore, not to mention breaking them. However the disoute is not between the UK and the RoI, but the UK and the EU. The UK may or may not break a treaty, it may or may not sign treaties and negotiate them before - but in any of these it demonstrates that it not only does not want but also must not ask Brussel for permission, but does what it wants anyway. Which in any conetsallaiton is sovereignity. They would compromise it if they allow Brussel to force them erecting international borders within their own state, that is a border regime between NI and the big isle.

Yes, one can scratch one's head over why they signed that NI protocol. Only one thing would be a sign of lacking sovereignty that you implied to exist in your post: if they would obey it.

Thats why I do not expec them to obey it. Obeing it would thwart a major argument for Brexit. Even Johnson cannot afford that, although they seem to let him get away with a lot.