California's new ammunition background check law in its first month stopped more than 100 people from buying bullets illegally, officials said late Monday as they struggled to deter more of the mass shootings that have roiled California and other states over the last week.

"Countless other prohibited persons were likely deterred from even trying to purchase ammunition that they cannot lawfully possess," Attorney General Xavier Becerra said in a court filing. He disclosed the early results in response to a gun owners' rights group attempt to block the law that took effect July 1.

A federal judge is expected to decide later this month whether to halt the law as a violation of the Second Amendment right to bear arms and other federal laws.

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The filing came as Gov. Gavin Newsom said the federal government should follow California's lead in requiring background checks for ammunition buyers.

"Guns don't kill people," Newsom said, noting that it also requires ammunition.

The Democratic governor convened a 90-minute emergency meeting with Becerra and several dozen law enforcement leaders, community members, civil rights leaders, researchers and emergency responders to grapple with what more the state can do to prevent mass shootings.

Aside from weekend slayings in El Paso, Texas, and Dayton, Ohio, they include one that left four dead, including the shooter, at a popular Northern California food festival late last month. The Democratic governor said the conversation is only beginning as he declined to outline specific steps, including whether he supports any of the several pending bills intended to toughen California's already strict gun laws.

Chuck Michel, an attorney representing the National Rifle Association and its California affiliate that sued to block the background checks, said he and the associations sympathize with mass shooting victims.

"But this ammo law is not gonna save any lives. You're not smoking out the violent felons. Violent criminals aren't going to buy ammunition and have a background check done," Michel said. "All of this red tape is just going to push people out of the sport and from owning a gun to defend their families."

Aside from the more than 100 who were prohibited, the state's filing says nearly 11,000 prospective buyers were denied immediate approval but were not determined to be barred from owning guns or buying ammunition. The state processed more than 57,000 such transactions in the first month, approving nearly 47,000 of them.

Buyers who already are in the state's firearm background check database now pay a $1 fee each time they buy ammunition, while others can buy longer-term licenses if they do not have certain criminal convictions or mental health commitments.

It took an average of less than five minutes to complete the background checks, the state's filing says.

It challenges the California Rifle & Pistol Association's assertion that the background checks take too long, are too burdensome and result in too many illegitimate rejections, given that "tens of thousands of ammunition transactions were processed in July alone."

"There is no substantial impediment," the state filing says. "Ammunition purchasers must pass an eligibility check that, in the vast majority of cases, delays a purchase by a few minutes."

There was a spike in calls to the state's customer support center in the first week, but those then dropped significantly, according to the filing. There were also "some technical issues," including delays in processing checks on buyers who had several first names, but the state's filing said that problem has since been corrected.