In an alarming victory for the gun lobby, Missouri’s Republican-controlled Legislature voted Wednesday to override Gov. Jay Nixon’s veto and enact a wholesale retreat from gun safety in the state.

The law will let citizens carry concealed weapons in public without a state gun permit, criminal background check or firearms training. It strips local law enforcement of its current authority to deny firearms to those guilty of domestic violence and to other high-risk individuals. And it establishes a dangerous “stand your ground” standard that will allow gun owners to shoot and claim self-defense based on their own sense of feeling threatened.

The measure has drawn no great national attention, but it certainly provides further evidence that gun safety cannot be left to state lawmakers beholden to the gun lobby. Democrats opposed to the Missouri bill called it a “perfect storm” of lowered standards for the use of deadly force and an invitation for people to be armed without responsible controls. The measure was enacted by the Republicans, despite strong public opposition and warnings about the threat to public safety from the state Police Chiefs Association. Everytown for Gun Safety, one of the groups fighting the gun lobby, noted that stand your ground laws result in disproportionate harm to communities of color.

Mr. Nixon, a Democrat, vetoed the measure in June, saying it would allow individuals with a criminal record to legally carry a concealed firearm even though they had been, or would have been, denied a permit under the old law’s background check. Mayors Sly James of Kansas City and Francis Slay of St. Louis warned against restricting the power of the local police to deny guns to those who commit domestic violence. They cited sharp spikes in domestic violence homicides in their cities, and they noted that the police would be left at greater risk by this bill.