The Republican-led Senate had approved the provision last week, but senators reversed themselves in a 22-9 vote after the NRA called on lawmakers to oppose the bill because of that amendment. The provision would have required firearms owners to report a stolen gun within 72 hours of learning about the theft.

Senate Republicans argued that it was unfair to require stolen firearms to be reported when state law doesn’t require the same for many other thefts. The St. Louis Democrat who sponsored the amendment said it was necessary to help crack down on urban crime, though after standing and controlling the debate for nearly five hours in an attempt to save the provision, she ultimately relented — noting that the overall bill, which seeks to nullify some federal gun laws, was destined to fail in court.

“We are changing course just because of one special interest group that decided to oppose. And now everyone decides to run,” said Sen. Jamilah Nasheed.

The NRA had not weighed in on the issue until the Senate adopted Nasheed’s amendment. In a posting on its website last week, the NRA said it has consistently opposed such measures, arguing that they could lead to a gun-owner registry by having owners tell police when guns are missing.

The bill’s sponsor, Sen. Brian Nieves, R-Washington, said the organization “misfired” on its opposition and mischaracterized the amendment. But he ultimately supported stripping the provision because the state doesn’t require many other thefts to be reported.

The NRA claimed that failing to report a stolen firearm would subject owners to a year in prison, a $1,000 fine and the loss of their concealed weapons permit — but those penalties weren’t in Nasheed’s amendment.

Senate President Pro Tem Tom Dempsey, R-St. Charles, said he supported stripping the amendment because of the potential for civil liability if a gun owner did not report a stolen weapon.

The amendment had been added to a broader measure that seeks to nullify some federal gun control laws — which courts have consistently ruled states cannot do — and impose possible civil fines or charges on federal agents who enforce such laws. Federal agents knowingly enforcing those laws could face civil penalties or prosecution for a crime punishable by up to a year in prison and a $1,000 fine.

“This is arguably the most powerful, strongest pro-Second Amendment bill in the United States,” said sponsoring Sen. Brian Nieves, R-Washington. “It’s like a Second Amendment dream come true.”

Courts’ consistent rulings against such laws haven’t stopped Missouri and other states from trying. The bill’s supporters point to the federal government’s decision not to challenge recreational marijuana laws in Colorado and Washington as grounds for the legislation.

Missouri Republicans began considering a measure to nullify gun laws last year after President Barack Obama called for expanded background checks and an assault weapons ban. A similar bill passed in 2013 but was vetoed by Democratic Gov. Jay Nixon.

The legislation would also allow designated school personnel to carry concealed weapons on school property after undergoing training. School districts would need to hold a public hearing before permitting concealed weapons in buildings, and designated staff could also choose to carry pepper spray.

Another provision of the bill would allow holders of concealed gun permits carry firearms openly, even in municipalities with ordinances banning open carry.

The bill would also lower the minimum age to get a concealed weapons permit to 19 from the current age of 21, and would state that health care professionals could not be required to ask or document whether a patient owns a firearm.

The bill needs one more vote in the Senate before moving to the House.