Police and FBI investigate near a vehicle in which two suspects were shot by police after a mass shooting in San Bernardino. Mike Blake / Reuters

Updated on December 3 at 5:15 p.m. EST

In the wake of mass violence, some Americans look to tighten gun laws because that’s something tangible, if politically difficult, that they can do—whether or not those new rules would have prevented a specific incident.

As Californians file into voting booths next November, they might see a ballot initiative inspired at least in part by mass shootings like the one in San Bernardino this week, which 14 people were killed and 21 injured.

California Lieutenant Governor Gavin Newsom announced the proposition in October at the San Francisco site of a 1993 shooting that claimed eight lives. And when he talked to The Los Angeles Times about his efforts, he referenced the 2012 Sandy Hook shooting in Connecticut, which claimed 26.

“Since Sandy Hook, I have sat back as a father and been mesmerized by the inability of the federal government to do anything substantively on gun safety,” Newsom said in a late-November interview.

In response, Newsom, a candidate for governor in 2018, seeks to tighten up his state’s existing gun laws. They’re already the toughest in the country: In 2013, the Law Center to Prevent Gun Violence—which helped write the new initiative—and the Brady Campaign to End Gun Violence gave California the highest marks in the nation for gun control.

The new initiative, which could be part of an unusually long roster of propositions considered in November, will require more than 360,000 signatures to make the ballot. It’s been characterized as “cobbled together” from bills that faltered in the state legislature, and the Sacramento Bee has a helpful summary of what it calls for:

It would ban the possession of large-capacity magazines—more than 10 rounds—and require anyone who currently has them to sell to a licensed firearm dealer, transfer them out of state or relinquish them to law enforcement to be disposed of.

The pending measure also would force those selling ammunition to be licensed like firearm dealers and require the purchasers to go through a background check. [Ed. note: California would be the only state in the nation to mandate background checks for those buying ammunition “at the point of sale.”] It would establish a process to recover guns from people prohibited from owning them because of their criminal record; mandate individuals whose guns were lost or stolen to report to law enforcement; and compel the state Department of Justice to notify the federal government when someone is added to the database of people barred from buying or owning a firearm.

The provision focusing on high-capacity magazines seems designed to prevent another mass shooting in California. These implements are characteristic of mass shootings: They may’ve been used in the San Bernardino shooting; a New York Times report describes the two shooters’ weaponry as “.223-caliber assault rifles and semiautomatic handguns.” And high-capacity magazines were used by Adam Lanza, the Sandy Hook shooter; James Holmes, who opened fire in an Aurora, Colorado, movie theater; and Seung-Hui Cho, the Virginia Tech shooter, among others.

States with stricter gun-control laws on the books have “significantly lower” gun deaths, per a 2011 Atlantic analysis. But whether that’s a causal or correlative link, and whether mass shootings can be wholly prevented by tough gun laws isn’t clear-cut. Gun laws may inhibit mass shooters the way they inhibit others who shouldn’t have access to a gun, such as those with felony convictions or who have been adjudicated to be dangerous to themselves or others. (Though it’s worth noting that loopholes in those laws allow many people to slip through the cracks.) California, too, has laws on the books that ban felons and those deemed dangerous from possessing guns. California’s laws also prohibit ownership by those who’ve been convicted multiple times of dangerously brandishing or otherwise “unlawfully” using a gun; who’ve been found not guilty of a violent felony by reason of insanity; who are “gravely disabled” by mental illness or seriously affected by alcoholism; and those who are “mentally disordered sex offender[s].” But some of the risk factors most commonly associated with potential mass shooters are less susceptible to regulation.

A New York Times analysis written after the Umpqua Community College shooting in October describes why mass shooters are often so hard to identify: They share the characteristics of so many other people. They’re typically single white men of varying political backgrounds, who’ve purchased their chosen weapons lawfully and may not get along so well with other people. Though they may have a mental illness, “most people with mental illness are not violent.” The Times put the difficulty of identifying mass shooters this way:

Weaving a profile of the public mass murderer, drawing on threads that have been identified, can reveal the broad contours of a certain type of individual. But those contours are indistinct enough to apply to countless others—the recluse next door with poor hygiene who never speaks—who will never pick up a gun and go out and murder.

Take a recent shooting in Congress’s backyard, at the Washington Navy Yard in 2013. Fawn Johnson noted in National Journal that no legislation championed by gun-control supporters could’ve stopped it. Federal rules bar only those who have been convicted of felonies, involuntarily committed to mental-health institutions, or found by a court to be either unable to manage their own affairs or to pose a danger to self or others from purchasing firearms. Absent those specific bars, shooters can pass through the existing background check system. “And unless this coun­try bans all per­son­al own­er­ship of guns,” Johnson wrote, “an­other mass shoot­ing will oc­cur.”

In response to Wednesday’s San Bernardino shooting, California’s voters may choose to support Newsom’s proposition with more gusto. As an Economist story noted after April’s shooting at a Charleston church, “many of us want to see lax gun-control behind these massacres, because gun control is a policy lever we can pull—at least in principle. A lack of reasonable gun control, many of us feel, is what the cause of the problem ought to be.”

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