Mich. Comp. Laws § 141.66

Sec. 6. Nothing in this act shall invalidate any bonds heretofore authorized or any proceedings heretofore taken to authorize the issuance of bonds by any county of the state, but all proceedings and elections heretofore since January 1, 1920, taken and held to authorize the issuance of bonds of any county, and all bonds heretofore issued under authority of a vote of a majority of the electors in said county, voting upon the question at an election held for that purpose are hereby validated, approved and confirmed.