Mich. Comp. Laws § 45.101

Sec. 1. A city situated in 2 or more counties may by resolution of its governing body or petition of 10% of its registered electors or 10,000 registered electors, whichever is the lesser have the question of adjusting the counties' boundaries so the entire city shall be included within 1 county placed on the ballot at the next general election held not earlier than 90 days from the certification of the resolution or receipt of the petition by the clerk of the local governing body.