Missouri constitution
Article IV: executive department
Section 19

The head of each department may select and remove all
appointees in the department except as otherwise provided in this constitution, or by
law. All employees in the state eleemosynary and penal institutions, and other state
employees as provided by law, shall be selected on the basis of merit, ascertained as
nearly as practicable by competitive examinations; provided that any honorably discharged
member of the armed services of the United States who is a citizen of this state
shall have preference in examination and appointment as prescribed by law.