Missouri constitution
Article IV: executive department
Section 11(b)

Whenever the governor transmits to the president pro tempore of
the senate and the speaker of the house of representatives his written declaration that
he is unable to discharge the powers and duties of his office, and until he transmits to
them a written declaration to the contrary, such powers and duties shall be discharged
by the lieutenant governor, or if there be no lieutenant governor, by the president pro
tempore of the senate, the speaker of the house, secretary of state, the state auditor, the
state treasurer, or the attorney general in succession, as acting governor. Whenever a
majority of a disability board comprised of the lieutenant governor, the secretary of
state, the state auditor, the state treasurer, the attorney general, president pro tempore of
the senate, the speaker of the house of representatives, the majority floor leader of the
senate, and majority floor leader of the house, transmits to the president pro tempore of
the senate and the speaker of the house of representatives their written declaration that
the governor is unable to discharge the powers and duties of his office, the lieutenant
governor, or if there be no lieutenant governor, the president pro tempore of the senate,
the speaker of the house, the secretary of state, the state auditor, the state treasurer or
the attorney general in succession, shall immediately assume the powers and duties of
the office as acting governor. Thereafter when the governor transmits to the disability
board his written declaration that no inability exists, he shall resume the powers and
duties of his office on the fourth day after he transmits such declaration unless a majority
of the disability board transmits their written declaration that the governor is unable
to discharge the powers and duties of his office to the supreme court within that four
day period, and the supreme court shall then convene to decide the issue. If the supreme
court within twenty-one days after receipt of such declaration, determines by a majority
vote of all members thereof that the governor is unable to discharge the powers and
duties of his office, the acting governor shall continue to discharge the same as acting
governor; otherwise, the governor shall resume the powers and duties of his office.