Wis. Stat. § 218.0138

A mediator or arbitrator is immune from civil liability for any good faith act or omission within the scope of the mediator’s or arbitrator’s performance of his or her powers and duties under s. 218.0136 or the arbitration plan referred to in s. 218.0137. Every act or omission of a mediator or arbitrator is presumed to be a good faith act or omission. This presumption may be overcome only by clear and convincing evidence.