California has some of the most restrictive gun laws in the U.S., so why haven’t the mass shootings stopped?

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U.S. lawmakers looking to curb gun violence after last week’s mass shootings in Texas and Ohio could take a lesson from California. The state has long had the most restrictive gun laws in the United States, but continues to see more mass shootings than anywhere in the country.

California has more than a hundred gun laws on its books. Many go back more than a decade, including a ban on assault weapons and restrictions on high-capacity magazines. The state has required background checks for all gun sales, including private transactions and firearms purchased at gun shows, since the 1990s. In 2016, it enacted “red flag” laws that allow police to seize firearms from people deemed a threat.

U.S. President Donald Trump offered support for both policies in the wake of shootings that left 31 people dead in El Paso, Tex., and Dayton, Ohio, with Mitch McConnell, Republican leader of the U.S. Senate, signalling he is open to passing new gun-control measures when senators return from a summer break in September.

But California’s experience raises questions about whether this type of legislation alone is enough.

Despite its stringent laws, California has seen 33 mass shootings since 2000, more than any other state. There have been three in the past nine months that have killed 15 people.

Law-enforcement officials and experts in gun violence say many of the measures California has put in place are considered among the most promising ways to reduce gun violence and deter mass shootings. But they have been hampered by a poor rollout.

Databases used for background checks have been plagued by missing information and lengthy backlogs. Gun-violence restraining orders that let police confiscate weapons from high-risk people – put in place after mass shootings in Isla Vista and San Bernardino – have been rarely used because many police departments and prosecutors weren’t even aware of them.

Mass shooters have continued to expose loopholes in California’s laws. Last fall, former Marine Corps machine gunner Ian David Long killed 11 people inside a bar in Thousand Oaks, a suburb of Los Angeles. Police had called in mental-health crisis workers to assess Mr. Long months before the shooting, but never tried to use the state’s red-flag laws to confiscate his guns.

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In 2017, a gunman banned from owning firearms because of a restraining order used two homemade AR-15 style rifles to kill six people and shoot children at a local elementary school in Tehama County. Several recent Californian mass shooters have been able to acquire magazines that could hold up to 75 bullets, despite the state’s long-standing ban on high-capacity magazines.

Earlier this year, California began limiting gun purchases to buyers who were at least 21 years old and requiring background checks to buy ammunition. But two of California’s mass shooters this year were still legally allowed to buy semi-automatic rifles, even though both were just 19 years old.

Newly unsealed search warrants showed the gunman who attacked a synagogue near San Diego in April appeared to have a hunting licence, which may be how he was able to pick up his AR-15 style rifle from a local gun store the day before the shooting. Those with hunting licences are allowed to buy rifles starting at the age of 18 under an exemption to the state’s new age restrictions.

Police say the teenager who killed three people at a weekend festival in Gilroy late last month purchased his AK-47 style rifle and high-capacity gun clips in neighbouring Nevada.

California has also been forced to revise its assault-weapon restrictions repeatedly to keep up with innovations from firearm manufacturers. It rewrote its assault-weapons laws for a third time in 2016, to close a “bullet button” loophole – named after a popular modification that had allowed gun owners to use a pointed object such as the tip of a bullet to quickly remove a magazine while still technically complying with the state’s restrictions on detachable magazines.

Gun-violence researchers say laws such as background checks and firearm restraining orders are among the most important measures to curb mass shooters. But California’s experience shows how important it is for lawmakers to not just pass new legislation, but make sure it is properly implemented.

“Background checks can return false negative results (fail to identify prohibited persons) when information on prohibiting events isn’t reported,” Garen Wintemute, an emergency-room physician who leads a violence research project at the University of California, Davis, wrote in an e-mail. “Gun violence restraining orders aren’t used often enough; they’re new, and not well known.”

Dr. Wintemute’s team is preparing to publish a study this fall describing ways in which background-check policies fall short and recommending reforms, but he declined to elaborate.

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California is home to an estimated 4.5 million legal firearms owners, but gun-violence restraining orders were used just 610 times in the first three years, with nearly half of them last year issued by a single county.

Santa Clara County deputy district attorney Marisa McKeown, a vocal proponent of the restraining orders, says her office has used them more than 40 times this year, up from just four in 2017. She regularly trains police officers on restraining orders and has encountered judges who have delayed issuing the emergency orders because they weren’t familiar with them.

“It’s an incredibly powerful tool. It fills a gap. It prevents shootings. It is effective,” says Ms. McKeown, whose region includes the site of last month’s mass shooting in Gilroy. “However, the police didn’t know about it.”

The biggest roadblock to California’s firearm restrictions, however, may be the legal challenges by gun-rights groups. Earlier this year, a federal court judge in San Diego briefly overturned California’s 19-year ban on high-capacity magazines in a ruling that referenced several cases of women terrorized by intruders after they ran out of ammunition and cited Nazi Germany’s restrictions on Jews owning weapons as an example of the dangers that come when governments forcibly disarm their citizens.

The court reinstated the ban a week later pending the state’s appeal. But in the eight days that the ban was lifted, the California Rifle and Pistol Association reported that gun owners in the state purchased “hundreds of thousands – if not millions” of high-capacity magazines in a buying spree the lobby group dubbed “Freedom Week.”

Many of California’s recent gun laws – including its assault-weapons bans and mandatory background checks for ammunition purchases that began this year – may ultimately end up being appealed to the U.S. Supreme Court, said Stanford University law professor John Donohue.

The court is poised to hear its first Second Amendment (the right to bear arms) case in nearly a decade this year. The case, involving a New York City law banning gun owners from transporting their handguns outside the city, could have major consequences for state and local gun restrictions – and for efforts by Congress to expand federal gun laws.

While much of focus of the Trump administration’s appointments of conservative judges such as Justice Brett Kavanaugh to the Supreme Court had been on what it will mean for state abortion laws, Dr. Donohue believes state and local gun-control laws may instead be country’s next major legal battle.

“In many ways, this is a much bigger deal than the abortion decision,” he said. State laws allowing access to abortion would still remain even if the Supreme Court overturns Roe v. Wade. “But if the gun decision is made on a federal constitutional basis, that would mean that California, and New York, and Illinois, will have to have the gun regulations of Alabama and Mississippi.”

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