Mich. Comp. Laws § 3.382

Sec. 2. The jurisdiction of said lands is hereby ceded to the United States of America: Provided, That this cession is upon the express condition that the state of Michigan shall retain concurrent jurisdiction, both civil and criminal, over persons on said lands, so far that all civil and criminal process issued by any court of competent jurisdiction or officers having authority of law to issue such process and all orders made by such court, or any judicial officer duly empowered to make such orders necessary to be served upon any person, may be executed upon said lands in the same way and manner as if jurisdiction had not been ceded as aforesaid.