Missouri Constitution
Article III - Legislative Department
Section 18 Appointment of officers of houses—jurisdiction to determine membership—power to make rules, punish for contempt and disor derly conduct and expel members.

Each house shall appoint its own officers; shall be sole judge of the qualifications, election and returns of its own members; may determine the rules of its own proceedings, except as herein provided; may arrest and punish by fine not exceeding three hundred dollars, or imprisonment in a county jail not exceeding ten days, or both, any person not a member, who shall be guilty of disrespect to the house by any disorderly or contemptuous behavior in its presence during its sessions; may punish its members for disorderly conduct; and, with the concurrence of two-thirds of all members elect, may expel a member; but no member shall be expelled a second time for the same cause.

Source: Const. of 1875, Art. III, Sec. 17.