Mo. Rev. Stat. § 536.100
Any person who has exhausted all administrative remedies provided by law and who is aggrieved by a final decision in a contested case, whether such decision is affirmative or negative in form, shall be entitled to judicial review thereof, as provided in sections 536.100 to 536.140, unless some other provision for judicial review is provided by statute; provided, however, that nothing in this chapter contained shall prevent any person from attacking any void order of an agency at any time or in any manner that would be proper in the absence of this section. If the agency or any board, other than the administrative hearing commission, established to provide independent review of the decisions of a department or division that is authorized to promulgate rules and regulations under this chapter fails to issue a final decision in a contested case within the earlier of:
then the person shall be considered to have exhausted all administrative remedies and shall be considered to have received a final decision in favor of the agency and shall be entitled to immediate judicial review as provided in sections 536.100 to 536.140 or other provision for judicial review provided by statute. In cases, whether contested or not, where the law provides for an independent review of an agency's decision by a board other than the administrative hearing commission and further provides for a de novo review of the board's decision by the circuit court, a party aggrieved by the agency's decision may, within thirty days after it receives notice of that decision, waive independent review by the board and instead file a petition in the circuit court for the de novo review of the agency's decision. The party filing the petition under this section shall be considered to have exhausted all administrative remedies.
§ 536.100, RSMo