Mo. Const. art. V, § 5

The supreme court may establish rules relating to practice, procedure and pleading for all courts and administrative tribunals, which shall have the force and effect of law. The rules shall not change substantive rights, or the law relating to evidence, the oral examination of witnesses, juries, the right of trial by jury, or the right of appeal. The court shall publish the rules and fix the day on which they take effect, but no rule shall take effect before six months after its publication. Any rule may be annulled or amended in whole or in part by a law limited to the purpose. [Effective - 02 Sep 1976 , see footnote]