But the measure has drawn sharp criticism from many law enforcement officials of all political stripes — including Second Amendment purists, who say it endangers public safety.
“It’s just a terribly written law,” Sheriff Brad Cole, a Republican from Christian County in the rural Ozarks region of the state, said last year, echoing the sentiments of other local officials.
In an affidavit filed in the state case in August, the special agent in charge of the Kansas City field division of the Bureau of Alcohol, Tobacco, Firearms and Explosives, 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nearly a quarter of state and local enforcement officials who worked directly with the agency — 12 of 53 officers — had withdrawn from joint collaborations.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 have begun to restrict federal access to investigative resources they have historically shared, including the Missouri Information Analysis Center, a state crime database, and the Kansas City Police Department’s records system, he said.
The bill’s supporters have argued that the new law is constitutional and does not prohibit federal agents from operating in Missouri. They have argued it only blocks state and local law enforcement officials from working on such cases without explicit proof that their actions will not contribute to the confiscation of guns from law-abiding citizens.
Gov. Mike Parson, a former sheriff, has suggested that the legislature should revisit the law to address the objections of law enforcement officials.
The Justice Department said it had filed the suit to assert a larger constitutional principle.
“A state cannot simply declare federal laws invalid,” said Brian M. Boynton, head of the Justice Department’s Civil Division, said.