Mo. Rev. Stat. § 414.022: Preemption by the state, political subdivisions may not regulate.

The state of Missouri hereby preempts the field of regulating the inspection of and providing specifications for any substance regulated by sections 414.012 to 414.152 and it shall be unlawful for any political subdivision to impose by ordinance, order, or regulation any restriction on the use or sale of any substance regulated by this chapter.