Wis. Stat. § 185.92: Effect of unauthorized acts.

No act and no transfer of property to or by a cooperative is invalid because made in excess of the cooperative’s power, except that such lack of power may be asserted in a proceeding by:

(1) A member, stockholder or director against the cooperative to enjoin any act or any transfer of property to or by the cooperative.

(2) The cooperative or its legal representative against any present or former officer or director.

(3) The attorney general against the cooperative in an action to dissolve the cooperative or to enjoin it from the transaction of unauthorized business.