Barca have two similar cases. They want to cancel Dembele's contract because he won't sign an extension. But that can only be done with his consent. Barca would probably be in breach of contract if they withdraw things like access to training, facilities etc.
They had another case a few weeks back where they were exploring trying to cancel a player's contract due to breach of contract - based on poor performance, physical condition, effort etc. The player responded by citing instances where he stayed behind late for extra training. Can't recall the guy's name, but it was discussed on Kieran Maguire's pod.