California has long played a pivotal role in the study of gun violence, maintaining a unique repository of detailed information on gun owners that it shares with researchers.

The National Rifle Association and other gun rights groups have filed lawsuits challenging that established practice. The lawsuits come as researchers confront an uptick in gun-related deaths, driven by a surge in homicides. They were filed a year after the NRA’s research director acknowledged at a private meeting that the group’s opposition to gathering such data has severely hampered gun violence research in the United States.

With narrow exceptions, all firearms transactions in California must go through licensed dealers, who relay information on purchasers that includes name, address, and date of birth to the California Department of Justice.

For over 30 years, the DOJ has shared this data with public health researchers, who have used it to try to untangle the connections between gun ownership and homicides, suicides, and other violence. They say this baseline information is key to understanding the risks and benefits of having a gun and, ultimately, to reducing injuries and deaths.

“California is special,” said David Studdert, a professor and gun researcher at Stanford Law School who focuses on the intersection of law and public health. “It’s not possible to do this kind of work elsewhere in the country. You need to be at the individual and household level to make the connection between the gun and a violent outcome. You can’t measure what you can’t see.”

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