U.S. Court of Appeals for the Eighth Circuit Judge James Loken on Friday seemed skeptical of Missouri’s defense of its law that restricts state police from enforcing certain federal gun laws.

At issue is Missouri’s Second Amendment Preservation Act, which lets individuals sue law enforcement agencies for enforcing federal gun-control statutes that Missouri has declared “invalid.” U.S. District Judge Brian Wimes ruled the state law invalidates provisions of the federal National Firearms Act and Gun Control Act in violation of the Constitution’s Supremacy Clause, which provides that federal laws take priority over any conflicting state laws.