Even if you buy this proposal - which like David I don’t - there’s a further problem, which falls into the category of the bleeding obvious but to which I’ve heard no coherent ERG answer.
This proposal explicitly depends on trust and very close legal cooperation and frameworks. So *you need the EU and Ireland to agree*.
If you actually want to keep the Irish border invisible by means of this sort of proposal (as opposed to paying lip service to the idea while trying to escape responsibility for hardening it) you have to have to have a strategy to persuade the EU/Ireland that this is workable.
What is that strategy?
