Mo. Rev. Stat. § 1.430: Invalidity of federal laws deemed an infringement.

All federal acts, laws, executive orders, administrative orders, rules, and regulations, regardless of whether they were enacted before or after the provisions of sections 1.410 to 1.485, that infringe on the people's right to keep and bear arms as guaranteed by the Second Amendment to the Constitution of the United States and Article I, Section 23 of the Constitution of Missouri shall be invalid to this state, shall not be recognized by this state, shall be specifically rejected by this state, and shall not be enforced by this state.