Michigan Compiled Laws, Chapter 600. Revised Judicature Act of 1961 § 600.1615

Sec. 1615. Any county in which any governmental unit, including but not limited to a public, municipal, quasi-municipal, or governmental corporation, unincorporated board, public body, or political subdivision, exercises or may exercise its governmental authority is the proper county in which to commence and try actions against such governmental units, except that if the cause of action arose in the county of the principal office of such governmental unit, that county is the proper county in which to commence and try actions against such governmental units.