Mich. Comp. Laws § 119.12

Sec. 12. If the charter or any amendment thereto of any district incorporated under the provisions of this act be approved, then 2 printed copies thereof with the vote for and against duly certified by the secretary of the commission, shall, within 30 days after the vote is taken, be filed with the secretary of state and a like number with the county clerk or clerks of the county or counties in which the district is located and shall thereupon become law.