Mich. Comp. Laws § 339.5811

Sec. 811. A municipality shall not establish or maintain local licensing requirements for the work classifications described in section 807(2) or work described in section 809(4). A governmental subdivision shall not prohibit a mechanical contractor that is licensed under this article from engaging in the work classification or classifications for which the mechanical contractor has a license, or a person described in section 809(4) from engaging in work for which that person is licensed or registered, unless the mechanical contractor is in violation of this act.