Mich. Comp. Laws § 26
In case of the conviction of the governor on impeachment, his removal from office, his resignation or his death, the lieutenant governor, the elected secretary of state, the elected attorney general and such other persons designated by law shall in that order be governor for the remainder of the governor's term.
In case of the death of the governor-elect, the lieutenant governor-elect, the secretary of state-elect, the attorney general-elect and such other persons designated by law shall become governor in that order at the commencement of the governor-elect's term.
If the governor or the person in line of succession to serve as governor is absent from the state, or suffering under an inability, the powers and duties of the office of the governor shall devolve in order of precedence until the absence or inability giving rise to the devolution of powers ceases.
The inability of the governor or person acting as governor shall be determined by a majority of the supreme court on joint request of the president pro tempore of the senate and the speaker of the house of representatives. Such determination shall be final and conclusive. The supreme court shall upon its own initiative determine if and when the inability ceases.
MCL 26