If there were any doubt that Maryland's new gun control law has the potential to reduce crime, a recent study by the Johns Hopkins Center for Gun Policy at the Bloomberg School of Public Health ought to dispel it. The researchers found that a handgun purchaser licensing requirement like the one Maryland just adopted has the potential to save many lives that otherwise would have been lost to gun violence.

The study examined the effect of the 2007 repeal of a Missouri law that required handgun purchasers to obtain a permit verifying their identity and their eligibility to own a firearm. After the law was repealed, murders in the state jumped 16 percent over the previous rate. After controlling for other factors, the researchers concluded that nearly all of the increase was attributable to the state's dropping its licensing requirement.

The sharp increase in homicides translated into between 55 and 63 additional murders a year in Missouri, a spike that wasn't matched in either its neighboring states or in the country as a whole. The inescapable conclusion from the state's anomalous situation was that dozens of people were being killed in Missouri every year who otherwise might still be alive if the law had remained in effect.

Hopkins professor Daniel Webster, the lead researcher on the project, described the results as "compelling confirmation that weaknesses in firearm laws lead to deaths from gun violence." Another expert, Philip Cook of Duke University's Sanford School of Public Policy, called it "the strongest evidence we have that background checks really matter."

In addition to ramping up the murder rate, researchers also found that repealing Missouri's law had provided a boon to criminals generally by making it easier for them employ so-called "straw purchasers" — people who buy guns with the intent of passing them on to others who are legally barred from owning them. After Missouri's licensing requirement was repealed, the time between the purchase of a gun and its appearance at a crime scene plummeted — an indication of increased straw purchase activity.

Last month, Mr. Webster told a Senate subcommittee in Washington that "immediately following the repeal of the law, the share of guns recovered by Missouri police agencies that had an unusually short time interval from retail sale to crime indicative of trafficking more than doubled." That suggested that criminals were taking advantage of the law's repeal to get guns much more easily than they could before.

Missouri's experience shows why Maryland lawmakers were wise to enact a handgun licensing system that will require prospective buyers to register with the state police and submit their fingerprints. Contrary to popular belief, criminals don't always — or even typically — get their guns by stealing them or buying them on the black market. If they can get them from a gun shop, either directly or through a straw buyer, they will.

We don't need to look to Missouri for evidence of that. In the months between the passage of Maryland's new gun control laws and the time they went into effect, the state experienced a gun buying frenzy that overwhelmed the state police's background check system. Despite beefing up staffing and taking other measures to reduce the backlog, the state was unable to complete background checks in anything close to the seven days required by law, and some gun dealers started releasing guns to their customers before the checks were completed, as they were legally allowed to do.

Only later did it turn out that in the final weeks before the new law went into effect, hundreds of guns ended up in the hands of people who should never have been allowed to buy them. One was purchased by a man later accused of using it to commit a carjacking, and others went to individuals with criminal records or histories of mental illness.

Fortunately, most of the weapons were recovered by police before they could be used to commit a crime. But the incident illustrated the same thing as Missouri's repeal of its licensing requirement: Gun control laws are not a plot to harass law-abiding gun owners but an effective means to keep deadly weapons out of the wrong hands. For that reason, Maryland lawmakers must continue to stand firm against the pressures from the gun lobby that would have this state follow Missouri's unhappy example.


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