Here are some of the key paragraphs from the Advocate General's Opinion. The Opinion opens a "third way". /1 
Dismissing the Government's (ridiculous) argument that the question is hypothetical "The practical... importance of the Court's answer is obvious". /2
There was a rather 'Polish' moment before the Court when Counsel for DExEU said that to adjudicate on the law would constitute an unwarranted interference in the UK's political process. Here's the response. /3
On the substance, the AG gives some examples of other recent decisions to revoke intentions to withdraw from international treaties. /4
There is no customary rule of law that you can revoke an intention to withdraw but it is still legitimate to have regard to the Vienna Convention as a "considerable source of inspiration." /5
Looking at the question as one of construction, you have to analyse Article 50 in its context. /6
Both the decision to withdraw and the decision to cancel the decision to withdraw are key manifestations of the sovereignty of a member state. /7
[I was emailed the Opinion by a journalist. No suggestion in the email to me that it was embargoed. It is now being suggested the Opinion is embargoed. I will stop tweeting extracts until the matter is clarified.]
