Now if Parliament gets its act together and manages to pass legislation that in the event of no deal, Article 50 is revoked then that'd be a different matter. Then again IMO there's very little chance of that happening because the majority of MPs (all DUP, nearly all Conservative, many Labour) apparently want Brexit.
That's how it should be done. But if that isn't done, Parliament passes a dozen resolutions saying it doesn't want a no deal and nothing else and no deal is inevitable ... PM could argue s/he was within his rights - indeed duties - to revoke article 50.
The point is probably moot if we're talking about BJ. It would be fascinating to watch Corbyn agonize over such a descision though. Morbid, but fascinating.
McHrozni