The case has been brought to ask the Scottish judges to refer the case to the ECJ
The judges said before that they couldn't do this before the UK actually decided to revoke, if it did.
The appeal was made mid-August to the Scottish Court and the decision is expected in a few weeks.
If that fails, campaigners could appeal again to the Supreme Court in London.
All this takes time
It also seeks to entangle the ECJ in forbidding E27 governments to do something in the future, if a theoretical possibility happens 
So the ECJ would have to decide whether to take it ... or back away hurriedly !
If they did, they would need time to hear the case and then make their decision
The first problem is UK politics:
neither the govt nor Labour have even hinted they wish to revoke A50
So if the govt decides to do so at the last moment, no time to start a court case then
In practice, if they did, most E27 members would agree - but fume ! - and the remainder could probably have their arms twisted / maybe even receive concessions from the UK
BUT
the main condition would be the UK agreeing it cannot call another Brexit ref for say 15 or 20 years - this is to stop the UK or anyone else using A50 to get better terms, or even to try to wreck the EU's normal business.
This would infuriate Leavers, because the next generation is likely to be very Remain
So it would probably kill Brexit forever.