It seems to me that you sue the unions for the return of the money that they illegally received, and the gov't agencies for a wrongful taking. I'd even think that a Section 1983 suit against the chief of each agency, the head of finance and the head of personnel for each agency, would be appropriate. It should be SIMPLE to get a TRO against the agencies, to be made permanent later.
It is SEIU, of course.
Democrats need that extorted money, doncha know.
Those Chesapeake waterfront mansions dont just pay for themselves, you know.