Mo. Rev. Stat. § 536.014
536.014 Rules invalid, when.
536.014. Rules invalid, when. — No department, agency, commission or board rule shall be valid in the event that:
(1) There is an absence of statutory authority for the rule or any portion thereof; or
(2) The rule is in conflict with state law; or
(3) The rule is so arbitrary and capricious as to create such substantial inequity as to be unreasonably burdensome on persons affected.
(L. 1997 H.B. 850) Effective 6-27-97