Mo. Rev. Stat. § 386.430

In all trials, actions, suits and proceedings arising under the provisions of this chapter or growing out of the exercise of the authority and powers granted herein to the commission, the burden of proof shall be upon the party adverse to such commission or seeking to set aside any determination, requirement, direction or order of said commission, to show by clear and satisfactory evidence that the determination, requirement, direction or order of the commission complained of is unreasonable or unlawful as the case may be.