The U.S. Supreme Court on Monday declined to hear Missouri’s appeal to reinstate a Republican-backed law aimed at blocking enforcement of certain federal gun regulations, leaving in place lower court rulings that struck down the law as unconstitutional. The 2021 Second Amendment Preservation Act sought to prevent Missouri officials from enforcing federal firearms laws that the state deemed to violate the Second Amendment.

Lower courts ruled the measure interfered with federal authority and violated the Constitution’s Supremacy Clause, which affirms that federal law overrides conflicting state laws. U.S. District Judge Brian Wimes, appointed by President Obama, blocked the law in 2023, and the 8th U.S. Circuit Court of Appeals upheld that decision in 2024.

Missouri filed its Supreme Court appeal on January 23, shortly after Donald Trump returned to the presidency. Despite Trump’s support for gun rights, his Justice Department urged the court not to take the case, stating that while parts of the law were unconstitutional, others raised more complex issues best addressed at the lower court level.

The law, passed by Missouri’s Republican-led legislature, imposed fines of up to $50,000 on officials who enforced federal gun laws deemed unconstitutional by the state. However, it failed to define which federal laws were invalid or who qualified as “law-abiding citizens.”

Federal officials argued the law obstructed firearms investigations by discouraging cooperation from local agencies. The Supreme Court’s refusal to hear the case leaves the lower court rulings intact and underscores federal supremacy in regulating firearms, even amid expanding Second Amendment protections.