Michigan Constitution of 1963, Art. VII, § 24

Sec. 24. Subject to this constitution, any city or village may acquire, own or operate, within or without its corporate limits, public service facilities for supplying water, light, heat, power, sewage disposal and transportation to the municipality and the inhabitants thereof.

Any city or village may sell and deliver heat, power or light without its corporate limits in an amount not exceeding 25 percent of that furnished by it within the corporate limits, except as greater amounts may be permitted by law; may sell and deliver water and provide sewage disposal services outside of its corporate limits in such amount as may be determined by the legislative body of the city or village; and may operate transportation lines outside the municipality within such limits as may be prescribed by law.