Mo. Rev. Stat. § 516.500

No action alleging a procedural defect in the enactment of a bill into law shall be commenced, had or maintained by any party later than the adjournment of the next full regular legislative session following the effective date of the bill as law, unless it can be shown that there was no party aggrieved who could have raised the claim within that time. In the latter circumstance, the complaining party must establish that he or she was the first person aggrieved or in the class of first persons aggrieved, and that the claim was raised not later than the adjournment of the next full regular legislative session following any person being aggrieved. In no event shall an action alleging a procedural defect in the enactment of a bill into law be allowed later than five years after the bill or the pertinent section of the bill which is challenged becomes effective.