A detachment removes territory from a city to the township. The detachment process has existed in Michigan law since 1909, when the Home Rule City Act was adopted. The process of detachment does not involve the State Boundary Commission. It is accomplished on the county level.

Boundary Adjustment is a Two-Way Street (.pdf)

Michigan Township News July 1991 

See Sections 6, 8, 9, and 13 (including lettered sections) of the Home Rule City Act: 

Home Rule City Act, Public Act 279 of 1909, MCL 117.1, et seq.