Mich. Comp. Laws § 92.1: Policemen; watchmen.

Sec. 1.

The council of any city may provide, by ordinance, for a police force and for the appointment by the mayor of such number of policemen and nightwatchmen as they may think necessary for the good government of the city and for the protection of the persons and property of the inhabitants; and may authorize the mayor to appoint special policemen from time to time, when in his judgment the emergency or necessity may so require.