Mich. Comp. Laws § 729.201

Sec. 1. Any city located in a county having a population of less than 500,000 having a court known as a police court, or otherwise, and having the jurisdiction in criminal cases of justices of the peace, or the jurisdiction to try and determine cases against persons charged with the violation of the charter or ordinances of the city, or both such jurisdictions, may adopt the provisions of this act by ordinance passed in accordance with the provisions of the charter of said city. Such adoption of this act may likewise be rescinded by ordinance.