Curbing gun violence is a complex challenge. While federal law requires licensed dealers to perform background checks for firearm sales, individuals may sell handguns without them. Laws requiring a license for all handgun purchases are one promising solution.

Licensing usually involves fingerprinting and more robust background checks. The 10 states that require licensing see fewer firearm deaths—from mass shootings, homicides, and suicides alike. “These are the laws that matter,” says Daniel Webster, ScD ’91, MPH, director of the Johns Hopkins Center for Gun Violence Prevention and Policy. “The benefits would be even greater were it not for weak gun laws in other states.”

That’s because states with licensing laws see crimes committed with guns purchased elsewhere, as the data reveal here. Expanding licensing laws nationwide, Webster says, would have a huge impact on gun trafficking and violence.

Loading dynamic infographic...

ABOUT THE DATA Flows are based on the 269,250 guns that were successfully traced in 2019 by the Bureau of Alcohol, Tobacco, Firearms and Explosives. A firearm is only traced if it is used in a crime, and then only if a law enforcement agency requests it. The process requires tracking a gun’s past sales and transfers through stacks of paper records; about 75 percent of traces are successful.

SOURCES: ATF (firearm recovery); Johns Hopkins Center for Gun Violence Prevention and Policy (state laws); CDC (death rates). All data for 2019.

Each line represents firearms that were recovered at a crime scene and subsequently traced back to a different state. Line thickness represents the number of guns traced between two states in 2019. Connections with fewer than 10 traces are omitted.

Gun flow volume legend ranging from 10 to 2000 plus

Color indicates the type of gun-acquisition law in each state, based on analysis by Johns Hopkins researchers. When sorting by "Strength of Law", states with strictest laws appear on the top.

Blue: License required for any handgun purchase; typically includes training, a background check, and a waiting period

Purple: Background checks required even for a private sale

Orange: Only the federal statute—background checks by dealers—applies

Takeaways

Proximity counts

Hawaii and other isolated states have few firearms entering or leaving; most guns entering California come from neighbors Arizona and Nevada.

Borders crossed

About a third of the guns traced in 2019 started in a different state from where they were recovered. In some places—including Connecticut and D.C.—most firearms came from out of state.

Directional flows

In states with stricter regulations (here, on the left), the lion’s share of out-of-state guns come from places where firearms are less tightly regulated (on the right).

Editor's note: This article was updated on June 24 to include a dynamic version of the graphic.

Pathways for Gun Crimes