[This was written as a response to a discussion on an article entitled “There’s a loophole in Article 50 that lets Britain back into the EU whenever we want” that argues that the UK can legally pull out of Brexit right up until the point that the agreement to leave actually comes into force. The original article is here: http://uk.businessinsider.com/brexit-how-does-article-50-work-2016-7 ]
To be honest, I don’t think it would be a legal question [at that point]. Aside from the fact that, already, any PM wanting to formally halt Brexit would have to go cap in hand and beg for political forgiveness for all the totally unnecessary cost and uncertainty that it has already caused the EU, Any PM who did this would be setting themselves up for a series of horrendous humiliations.
Say the process went on until 2020. By the end of 2020 EU27 would have agreed, without the UK, a new 7-year budget for 2021-2028, which did not include the UK or its rebate. This would mean a PM would have to basically agree to the UK element being tacked on to it without any say in it, and certainly without a rebate included. In the interim, there may also be proposals for treaty change to renew and reinvigorator the Union, and the UK would have to sign up wholesale to these. If there were treaty changes, they would almost certainly take the opportunity to also remove the UK-specific provisions such as not signing up the the Euro, opt-outs in Justice and Home Affairs, and so on. They would also probably extend Qualified Majority Voting, thus removing the power of veto in important areas, and will almost certainly try to strengthen common foreign and security policy. The UK would again have to accept these.
Perhaps more importantly though, the UK would have to sit and eat humble pie and get nothing out of negotiations for the next 5-10 years until it had been politically rehabilitated. I just don’t think any PM would sign up to that, even in the face of the grim consequences of Brexit.
I think we need to be really careful of pinning our hopes on something rescuing us post-Article 50. They may be legal, but they are politically almost impossible. Another one is some politicians’ calls for a referendum on the final deal. We won’t have a say on the final deal. Either we take it, or we reject it and the time runs out and we’re out without a deal. It’s a total political red herring in my view. We must stop Article 50 being invoked. Anything else means leaving.