WASHINGTON — A federal judge in Kansas City on Tuesday struck down a Missouri law that restricted local and state law enforcement agencies in carrying out federal gun laws, ruling that the statute violated the Constitution and posed a grave threat to public safety.
Judge Brian C. Wimes of the Western District of Missouri ruled that the Second Amendment Protection Act, passed in 2021 by the Republican-controlled state legislature, represented a blatant attempt to illegally usurp the federal government’s constitutional right to enforce federal laws without state interference.
In his 24-page decision, Judge Himes wrote that Missouri is now “prohibited from any and all implementation and enforcement” of the law, which had allowed gun owners to seek damages of up to $50,000 from local police and sheriff’s departments that enforced federal gun laws deemed to conflict with Second Amendment rights.
The law — passed as part of a right-wing backlash to President Biden’s pledge to press for new gun control legislation — was popular with the state’s Republican politicians but faced skepticism from conservative law enforcement officials who said it hampered their capacity to fight surging gun violence in the state.
“We are gratified by the court’s decision,” Attorney General Merrick B. Garland said in a statement, adding that it would “allow federal, state and local law enforcement in Missouri to work together to keep their communities safe from gun violence.”
Judge Wimes, an Obama appointee, expressed alarm in his ruling that some local and state departments had withdrawn from joint federal task forces in the wake of the law and had refused to use weapons databases administered by the federal Bureau of Alcohol, Tobacco, Firearms and Explosives.
In an affidavit filed in a state case in August 2021, the special agent in charge of the Kansas City field division of the A.T.F. reported that nearly a quarter of state and local enforcement officials who worked directly with the agency — 12 of 53 officers — had withdrawn from joint collaborations. In addition, state and local agencies had begun to restrict federal access to investigative resources they had historically shared, including the Missouri Information Analysis Center, a state crime database, and the Kansas City Police Department’s records system, the agent said.
Judge Wimes directed law enforcement officials in the state to “lawfully participate in joint federal task forces” and share information with the federal government without fear of financial penalties.
Missouri’s Republican attorney general, Andrew Bailey, vowed “to defend this statute to the highest court.” He said the state anticipated “a better result” from federal appellate courts.
“The Second Amendment is what makes the rest of the amendments possible,” Mr. Bailey said.
The Justice Department sued Missouri in February 2022, arguing that the state’s law, rammed through over the objections of Democrats, violated the supremacy clause of the Constitution, which forbids states to override federal statutes.
The bill’s supporters argued that the new law was constitutional and did not prohibit federal agents from operating in Missouri. They have contended that the measure only blocked state and local law enforcement officials from working on cases without explicit proof that their actions would not contribute to the confiscation of guns from law-abiding citizens.
But even supporters of the law have suggested that it might have gone too far. Shortly after signing the measure, Gov. Mike Parson of Missouri, a Republican and a former sheriff, floated the idea that the legislature should revisit it to address the objections of law enforcement officials.
That did not happen. And two of the state politicians most closely associated with the bill were catapulted to higher federal office after highlighting their support for it.
Eric Burlison, the state senator who sponsored the law, was elected to a House seat last year. Eric Schmitt, the state’s former attorney general — who defended the law — was elected to the Senate.