Wis. Stat. § 103.87

No employer may discharge an employee because the employee is subpoenaed to testify in an action or proceeding pertaining to a crime or pursuant to ch. 48 or 938. On or before the first business day after the receipt of a subpoena to testify, the employee shall give the employer notice if he or she will have to be absent from employment because he or she has been subpoenaed to testify in an action or proceeding pertaining to a crime or pursuant to ch. 48 or 938. If a person is subpoenaed to testify in an action or proceeding as a result of a crime, as defined in s. 950.02 (1m), against the person’s employer or an incident involving the person during the course of his or her employment, the employer shall not decrease or withhold the employee’s pay for any time lost resulting from compliance with the subpoena. An employer who violates this section may be fined not more than $200 and may be required to make full restitution to the aggrieved employee, including reinstatement and back pay. Except as provided in this section, restitution shall be in accordance with s. 973.20.