The agreement contains a commitment by the British and Irish governments to develop "close cooperation between their countries as friendly neighbours and as par

The agreement contains a commitment by the British and Irish governments to develop "close cooperation between their countries as friendly neighbours and as partners in the European Union". It's hard to see how we can do that as, er, not members of the European Union. This is the standard NI-border-tail-wagging-dog argument that you can't have Brexit at all because of wording in the GFA, but it's fundamentally flawed in two different ways. Firstly, your quote of the GFA is selective. Read the words just before the ones you mentioned, which fundamentally change the meaning. Secondly, both the UK and Ireland are signatories to the EU treaties, including the TFEU that provides for withdrawal of a member state under Article 50. As a matter of international law, to the extent that any earlier treaty between those parties is contradicted by a later treaty to which they are also signatories, the later one takes precedence. (This is why I noted before that the legal technicalities are debatable.) I agree with the spirit of the rest of your comment, in that advocates of Brexit need to get their story straight so there are concrete discussions to be had, so I won't comment further on those points here.