Mich. Comp. Laws § 408.1109

Sec. 9. (1) Except as otherwise provided in subsection (2), the provisions of this act shall not apply to contracts entered into or the bids made before the effective date of this act. (2) This act does not apply to a state project if the state project was paid for, in whole or in part, from revenue from a millage that meets both of the following conditions: (a) The millage was authorized under the revised school code, 1976 PA 451, MCL 380.1 to 380.1852. (b) The millage was authorized before the effective date of this act.