Mo. Rev. Stat. § 1.450: Enforcement of federal laws that infringe on right to keep and bear arms prohibited.

No entity or person, including any public officer or employee of this state or any political subdivision of this state, shall have the authority to enforce or attempt to enforce any federal acts, laws, executive orders, administrative orders, rules, regulations, statutes, or ordinances infringing on the right to keep and bear arms as described under section 1.420. Nothing in sections 1.410 to 1.480 shall be construed to prohibit Missouri officials from accepting aid from federal officials in an effort to enforce Missouri laws.