Wis. Stat. § 905.01: Privileges recognized only as provided.

Except as provided by or inherent or implicit in statute or in rules adopted by the supreme court or required by the constitution of the United States or Wisconsin, no person has a privilege to:

(1) Refuse to be a witness; or

(2) Refuse to disclose any matter; or

(3) Refuse to produce any object or writing; or

(4) Prevent another from being a witness or disclosing any matter or producing any object or writing.