Mich. Comp. Laws § Article IV § 29: Local or special acts.

Sec. 29.

The legislature shall pass no local or special act in any case where a general act can be made applicable, and whether a general act can be made applicable shall be a judicial question. No local or special act shall take effect until approved by two-thirds of the members elected to and serving in each house and by a majority of the electors voting thereon in the district affected. Any act repealing local or special acts shall require only a majority of the members elected to and serving in each house and shall not require submission to the electors of such district.