Mich. Comp. Laws § 3.885
It is recognized that any participating jurisdiction that agrees to render mutual aid or conduct exercises and training for mutual aid will respond as soon as possible. It is also understood that the participating jurisdiction rendering aid may withhold or recall resources to provide reasonable protection for itself, at its discretion. To the extent authorized by law, each participating jurisdiction will afford to the personnel of the emergency contingent of any other participating jurisdiction while operating within its jurisdiction limits under the terms and conditions of this agreement and under the operational control of an officer of the requesting participating jurisdiction the same treatment as is afforded similar or like human resources of the participating jurisdiction in which they are performing emergency services. Staff comprising the emergency contingent continue under the command and control of their regular leaders but the organizational units come under the operational control of the emergency services authorities of the participating jurisdiction receiving assistance. These conditions may be activated, as needed, by the participating jurisdiction that is to receive assistance or upon commencement of exercises or training for mutual aid and continue as long as the exercises or training for mutual aid are in progress, the emergency or disaster remains in effect, or loaned resources remain in the receiving participating jurisdictions, whichever is longer. The receiving participating jurisdiction is responsible for informing the assisting participating jurisdiction when services will no longer be required.
MCL 3.885