Ok, rephrasing this a little; my comment was that there are grounds for scrutiny of Brexit timeline (with EU) if it looks as though the end result will be UK either out of EU with access to CM whilst meeting all relevant criterior to qualify, or total u-turn.
There is noting except the A50 deadline. Current talk of deadlines for moving on to stage 2 are instrumental, not legal.
This is likely, but it's not written anywhere. That is why this exists: https://www.crowdjustice.com/case/strengthening/