The workers must not have had any legal representation or advocacy. If there was such legal representation involved on behalf of the workers, those lawyers must have been owned by the unions.
The workers should be able to sue for all union fees illegally taken from them.
It’s for situations like this one, that the majority of workers today want nothing to do with a Labor Union when the choice is their own. You will always have at least 33% that obediently follows the herd no matter what happens, and keeps their misplaced loyalty in all Labor Unions.
Some Unions are beneficial, many others are corrupt.