The US Supreme Court declined on Friday to block a district court ruling that a Missouri law that attempts to invalidate federal firearm law within the state is unconstitutional. Missouri applied to Justice Brett Kavanaugh to stay the lower court ruling.

Justice Clarence Thomas noted in the order that he would have granted the application to the court. Justices Neil Gorsuch and Samuel Alito stated in the order that:

With the understanding that the district court “prohibited” only “implementation and enforcement” of H. B. 85 by the State of “Missouri and its officers, agents, and employees” and “any others in active concert with such individuals,” App. to Emergency Application 29a, I agree with the denial of the application for a stay under the present circumstances. An injunction purporting to bind private parties not before the district court or the “challenged” provisions “themselves,” however, would be inconsistent with the “equitable powers of federal courts.” Whole Woman’s Health v. Jackson, 595 U. S. 30, 44 (2021).

In July 2021, Missouri Governor Michael L. Parson signed the Second Amendment Preservation Act (SAPA) into law. The law declares certain federal gun laws “invalid” if no Missouri state-level equivalent exists. In addition, SAPA carries a fine of $50,000 for each attempt to enforce such federal gun laws. In response to the passing of SAPA, the US DOJ sued to challenge its constitutionality.

At the district court level, US District Judge Brian C. Wimes ruled that SAPA violates the Supremacy Clause of the US Constitution and the doctrine of intergovernmental immunity. Wimes found that SAPA violates the Supremacy Clause because it tries to invalidate federal law. The Supremacy Clause states that federal law takes precedence over state laws and prohibits states from interfering with the federal government’s exercise of its constitutional powers. Additionally, Wimes ruled that the law violates the doctrine of intergovernmental immunity by impeding the operations of constitutionally enacted federal laws. These federal laws are the National Firearms Act and the Gun Control Act. Under the doctrine, state legislatures cannot invalidate or disregard federal statutes.