Many nuns belong to communities that own thier own property. The do not depend on the local bishop for economic support. The bishop cannot kick them out of their convents. The left wing radical nuns won’t leave because they live comfortable lives and have three hots and a cot. I doubt if they are Catholic or if they consider themselves to be Catholic. I think public excommunication would be a good idea. Let them call themselves Episcoplalians or Veternarians or whatever.
Do these nuns go to confession and take communion? What priest is cooperating with that?