The State Laws That Are Most Effective at Stopping Mass Shootings

With casualties mounting after the shooting in Uvalde, Texas, a health scholar’s research has found that enacting a few state policies can reduce gun violence by a third. 

At least 19 children and two adults are dead after a gunman opened fire inside Robb Elementary School in Uvalde County, Texas, on Tuesday. The massacre marks the 27th school shooting in 2022, according to Education Week, and the deadliest one since 2012, when a gunman killed 20 children and six adults at Sandy Hook Elementary School in Newtown, Connecticut. It also brings the total number of all mass shooting events in the US this year to 213, according to data from the Gun Violence Archive.

The tally has continued to mount in America — far surpassing the count in any other country — even as experts and research point to gun control policies that can prevent mass shootings, or at least reduce the number of casualties, if they are enacted.

“To be very honest, we have enough information right now to pass meaningful policy,” says Michael Siegel, a professor at the Tufts University School of Medicine who has studied the impact of gun laws on firearm violence. “To me, the main [barrier] is the political will, and why policymakers are not willing to stand up to the NRA.”

In 2020, while he was at Boston University, Siegel led a study looking specifically at the link between various types of local gun control laws that were in effect between 1976 and 2018, and the frequency and severity of mass public shootings (those that resulted in at least four victims and in which perpetrators killed indiscriminately in a public space). His team identified eight specific types of gun policies among the 89 laws, including assault weapon bans, large-capacity magazine bans, permit requirements, red-flag laws, universal background checks and laws prohibiting gun possession by people with a history of a violent misdemeanor crime.

Controlling for variables like socioeconomic factors and gun-ownership rates, the team concluded that two types laws have been most effective: State laws that require a permit to buy a firearm were linked to 60% lower odds of a mass public shooting happening, while a ban on large-capacity magazines could lower fatalities by 38% and nonfatal injuries by 77% when a mass shooting does take place. Siegel says these laws would be most effective when passed together, and ideally as part of a broader set of five basic gun policies.  

Bloomberg CityLab spoke with Siegel about his study, and gun safety more generally. The interview has been lightly edited for clarity.

What are the aspects of a mass public shooting that policymakers should consider?

So the first thing we looked at was what type laws are effective in preventing mass shootings from occurring in the first place. And the second aspect we looked at is, if an event does occur, are there laws that can be effective at reducing the number of casualties, specifically deaths? And we found that there were two laws that were effective, but they weren't effective for the same thing.

Laws that require that people have a permit in order to own or purchase a gun were effective in reducing the occurrence of a mass shooting in the first place. The second law that was effective were limits on the magazine capacity — specifically laws that limit magazine capacity to less than 10 rounds in detachable magazines. Those were not effective in preventing mass shootings, but they were effective in reducing the number of casualties when a mass shooting occurs.

From previous research, we found that two of the most effective types of laws to prevent firearm homicide generally, [not just mass public shootings] were permit laws and universal background checks. It is not surprising the same set of policies that make it much more difficult for criminals, essentially, to get weapons are, are laws that are going to be effective both in reducing firearm homicide and mass shootings in particular.

So in a sense, there really isn't a difference. The only difference really was specifically related to the number-of-casualty piece of mass shootings, the magazine limits do come into play. Because, you know, if you walk in with a 30-round magazine, you can shoot 30 rounds before you have to reload.

It is interesting though that your 2020 study concluded that universal background checks alone weren’t as effective as permit laws. Can you explain?

So you're correct, and part of the reason for that is kind of a statistical issue. Almost every state that has passed a permit requirement also has universal background checks. [What is effective] is the combination of the two, and what we're really finding is that states that only have background checks without permits, that just isn't as effective. 

What is the basic set of policies that you believe every state should pass?

What we really need is what I would call a suite of basic policies. In other words, not one policy, but a set of policies that all work together to cover different aspects of the problem. And my conclusion from what we have available now is that there are five baseline policies that every state should have.

Those are basically the three that we've talked about: a permitting mechanism, universal background check and a limit on the magazine capacity. Number four is a law that basically says that anyone who has committed a violent crime —we don't care what level it is — cannot access a gun. Not just a felony crime, but also a misdemeanor crime because federal law already prohibits people who committed a felony from possessing a gun. The problem is that there are a lot of violent crimes that just don't rise to the felony level. For example, a lot of domestic violence crimes are just prosecuted as misdemeanors. A lot of crimes — somebody threatened to kill someone, or cyber harassment or stalking — are misdemeanors.

Then the fifth law that every state should have is a red flag law, or an extreme risk protection order law. That is so important because in most mass shootings, there is some warning sign that the perpetrator has given. It's almost always the case that there was some history of threatened violence or planned violence. The red flag law allows law enforcement to take action when there is credible evidence that somebody does pose risk, and that may or may not be taking their gun away, but at the very least there's an investigation and a court hearing that bring this to the attention of the authority so that it doesn't sneak under the radar.

Would these have a larger effect enacted at the federal level?

Obviously that would be the most effective, but whether Congress has political will to do that there, I don't know. But if every state had those those five laws, our model predicts that would be about a 35% reduction in firearm homicide, which is a huge effect. We're basically talking about reducing one out of every three firearm homicide fatalities, and that's more than 10,000 people a year.

It's going to have an effect across the board. It's going to reduce firearm homicides. It's going to reduce homicides by young people. It's going to reduce mass shootings. The number one factor in firearm homicide is the possession of a gun. You know, if you don't possess a gun, you can't commit a firearm homicide, by definition.

But there is one law that your study suggests is not effective. Which one is that?

It may seem kind of counterintuitive or surprising, but laws that ban assault weapons don't seem to have any impact. I think what we learned from our research is, it's not the what, or the type of weapon; it's the who — who has the weapons. The most important aspect of firearm policy based on our researching is having the most sensitive and specific criteria for what types of people are the most at risk, and keeping guns out of their hands. The bottom line is that there's nothing special about an assault weapon that allows it to be more lethal in, for example, a school shooting situation. What does have an effect is the magazine capacity.

The other problem with assault weapon bans is that they're not supported by most gun owners. Gun owners are concerned about keeping guns out of the hands of criminals or potential criminals. So the beauty of our findings is that the types of laws that we're finding as most effective are precisely the kind of laws that gun owners support. I mean, most gun owners view gun ownership as a responsibility.

There's really only one barrier, and that's that a lot these lawmakers are afraid of the NRA.