Wis. Stat. § 133.14: Illegal contracts void; recovery.

All contracts or agreements made by any person while a member of any combination or conspiracy prohibited by s. 133.03, and which contract or agreement is founded upon, is the result of, grows out of or is connected with any violation of such section, either directly or indirectly, shall be void and no recovery thereon or benefit therefrom may be had by or for such person. Any payment made upon, under or pursuant to such contract or agreement to or for the benefit of any person may be recovered from any person who received or benefited from such payment in an action by the party making any such payment or the heirs, personal representative or assigns of the party.