I don’t know, but maybe someone with experience in contract law may post. To me it seems criminal.
I think there could be a two phase prosecution.
Phase 1: Prove there was criminal collusion between elected Democratic officials and the Unions in an attempt to defraud the public.
Phase 2: Prosecute the Unions and the Democrats under the RICO statute for racketeering and seize assets.
The the State of Wisconsin could use the proceeds to close the budget gap.