Wis. Stat. § 302.43

Every inmate of a county jail is eligible to earn good time in the amount of one-fourth of his or her term for good behavior if sentenced to at least 4 days, but fractions of a day shall be ignored. An inmate shall be given credit for time served prior to sentencing under s. 973.155, including good time under s. 973.155 (4). An inmate who violates any law or any regulation of the jail, or neglects or refuses to perform any duty lawfully required of him or her, may be deprived by the sheriff of good time under this section, except that the sheriff shall not deprive the inmate of more than 2 days good time for any one offense without the approval of the court. An inmate who files an action or special proceeding, including a petition for a common law writ of certiorari, to which s. 807.15 applies shall be deprived of the number of days of good time specified in the court order prepared under s. 807.15 (3). This section does not apply to a person who is confined in the county jail in connection with his or her participation in a substance abuse treatment program that meets the requirements of s. 165.95 (3), as determined by the department of justice under s. 165.95 (9) and (10).