That is fairly obvious: In an EU court by an EU citizen who has been disadvantaged by an EU decision.
At the end of the day it's common sense that the 'spirit' of EASA is that there should be a common standard - so to revoke recognition for purely political reasons is wrong. Ok, so the CAA has left EASA, they can't now issue new EASA licences, but their old ones were done to EASA standards, in many cases in EASA countries with EASA examiners so to say that they somehow no longer meet that standard is farcical.