Mich. Comp. Laws § 32.655

Sec. 255. In case of war, or a national emergency, when the national guard may be in the military service of the United States, the defense force shall be ready and able to protect the state in case of insurrection, invasion, disaster or other emergency, actual or imminent. In such case the governor, as commander-in-chief, may use the defense force augmented if necessary by all or a part of the unorganized militia not responsive to the orders of the president for the time being. The determination of the governor that an emergency exists or is imminent is conclusive.