Mo. Rev. Stat. § 71.286

Notwithstanding any other provision of the law to the contrary, no state law, city, town or village ordinance shall regulate the exhibition of a properly displayed United States flag. For the purposes of this section, the term "properly displayed" shall mean that the flag contains no additional design or embellishment and is displayed consistent with the provisions of Title 4 U.S.C. Sections 1-10, pursuant to the normally accepted guidelines for the display of the United States flag.