That's contrary to this (but more recent, in fact, it isn't law right now):

https://www.businessinsider.nl/uk-supreme-court-article-50-n...

And I note that it requires unanimous agreement between all the other member states, which is a very rare thing. So a very thin maybe.

Same publication, today: http://uk.businessinsider.com/eu-brexit-resolution-article-5...

Well, here's to hoping. But that's very thin ice. Maybe it will grow a bit thicker in the next two years.

Yeah, I could see it going the other way as well. Easy for 1 or more member states to say "Why should we let you back? You're always asking for other special deal."