KANSAS CITY (AP) — A law forbidding local police from enforcing federal gun laws in Missouri is hampering efforts to protect the public, federal authorities say.A blistering court brief filed Tuesday by the U.S. Department of Justice outlines multiple examples. The brief said that after an Independence police officer was killed in a shootout in September, state law enforcement initially refused routine federal assistance in tracing the murder weapon.The Justice Department says the Missouri state crime lab, operated by the Highway Patrol, also is refusing to process evidence that would help federal firearms prosecutions.The Missouri Information and Analysis Center, also under the Highway Patrol, no longer cooperates with federal agencies investigating federal firearms offenses. And the Highway Patrol, along with many other agencies, have suspended joint efforts to enforce federal firearms laws.The Justice Department's brief comes in an ongoing&nbsp;<a href="https://apnews.com/article/joe-biden-mo-state-wire-michael-brown-st-louis-gun-politics-3c5e14ad275f3c6f0b08e201db5b51cd">lawsuit&nbsp;</a>challenging the state gun law, filed by St. Louis City, St. Louis County and Jackson County.<a href="https://apnews.com/article/laws-gun-politics-missouri-35bd985b9cc7bf0881b04372af62eff1">A Cole County court's decision upholding the law&nbsp;</a>is being appealed to the Missouri Supreme Court.The brief says the law “poses a clear and substantial threat to public safety" and has “seriously impaired the federal government’s ability to combat violent crime in Missouri.”The law declares “invalid” many federal gun regulations that don’t have an equivalent in Missouri law. These include statutes covering weapons registration and tracking, and possession of firearms by some domestic violence offenders.Local departments are barred from enforcing them, or risk being sued for $50,000 by private citizens who believe their Second Amendment rights have been violated.Police are also prohibited from giving “material aid and support” to federal agents and prosecutors in enforcing those “invalid” laws against “law-abiding citizens” — defined as those who Missouri law permits to have a gun.The Justice Department, Democrats and other critics of the law, signed in June by Republican Gov. Mike Parson, say it’s blatantly unconstitutional. The brief appears to include the most extreme examples to date of the measure’s toll on law enforcement.It says the law “is not only damaging valuable institutional relationships for enforcing firearms laws, but also increasing dangers in the field across a broad array of law enforcement operations.”A Highway Patrol spokesman declined to comment, citing pending litigation.A spokeswoman for Parson didn’t immediately comment. Republican Missouri Attorney General Eric Schmitt’s office, which is representing the state in the challenge to the gun law, hasn’t yet filed a brief in the appeal.

Feds: Gun law poses 'clear and substantial threat' in Kansas City