Mo. Rev. Stat. § 622.120
Each administrative law judge and each person appointed to office or employment by the governor or by the division shall, before entering upon the duties of such person's office or employment, take and subscribe to an oath or affirmation to support the Constitution of the United States and of this state, and to faithfully and honestly discharge the duties of such office. No person shall be eligible to appointment or shall hold the office of administrative law judge, or be appointed by the division, or hold any office or position under the division, who holds any official relation to any common carrier, railroad corporation, street railroad corporation, transportation of freight or property company, carrier, corporation or person subject to any of the provisions of this chapter or chapter 387, 388, 389, 390 or 391, or who owns stocks or bonds therein, or who has any pecuniary interest therein.
§ 622.120, RSMo