Federal laws on the appropriate age to buy a gun are confused and nonsensical. You have to be 21 to buy a handgun from a federally licensed dealer. But if you’re 18, you can buy the same gun from a seller who doesn’t have a license. This has the perverse effect of forcing young people to buy handguns from sellers who — because they aren’t licensed — don’t have to conduct background checks.

Moreover, federal law allows licensed gun dealers to sell rifles to people as young as 18. Unlicensed sellers can sell the same gun to anyone regardless of age, even a 14-year-old. And while federal law prohibits people younger than 18 from possessing a handgun, nothing in the law prevents younger teens or even tweens from possessing a rifle.

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State laws close some of these loopholes, but not all. In Utah and Montana, there are no age restrictions on buying or possessing a handgun. In Mississippi and South Carolina, even juveniles can buy and possess a rifle.

At a minimum, we should have a uniform gun age that doesn’t depend, as federal law does, on the identity of the seller. We should also consider raising the minimum age to buy or possess (without adult supervision) a firearm to 25.

People under 25 are responsible for a disproportionate amount of America’s gun violence. According to data collected by the FBI, nearly 50 percent of all gun homicides are committed by people younger than 25. Most of those perpetrators are 18 to 24.

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Mass shooters are often young, too. What common thread runs through the high-profile mass shootings in Charleston, S.C.; Aurora, Colo.; and Tucson? All of the killers were under 25, and all of them had bought their guns legally from dealers. Gunmakers market their wares to young people, often featuring minor children with guns in advertisements. The late NRA president Charlton Heston exhorted gun owners to introduce “a young person to the fun and satisfaction of shooting” as a way “preserve freedom for future Americans.”

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Guns in the hands of young people lead not only to more crime but also more successful suicide attempts. About 38 percent of all suicides by people under 21 are committed with a gun. Because guns are far more effective than any other method, reducing access to guns for young people can reduce the number of suicides. The three leading causes of death among young people are unintentional injury, suicide and homicide. Sadly, guns play a role in each.

There is a reason people under 25 are dangerous with guns. The scientific literature over the past two decades has demonstrated repeatedly that the brain does not fully mature until the mid-to-late 20s. Last to mature is the prefrontal cortex, the part of the brain responsible for making intelligent, long-term decisions; for weighing risks and benefits; and for controlling impulses.

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Until the prefrontal cortex becomes dominant, the young brain is ruled by the limbic system, which is the emotional center. The already mature limbic system receives impulses far more quickly than the slowly developing prefrontal cortex, explaining why this age group is known for all sorts of risk-taking behaviors, both good and bad.

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That’s why young people tend to be innovators. It also explains why they are more likely to make foolish heat-of-the-moment decisions than many older, more mature adults.

Using brain maturation as a basis for age cutoffs is smart policy. Rental car companies won’t rent (or charge higher prices) to people younger than 25 because the actuarial tables clearly show that younger drivers have significantly higher accident rates. But what underlies that statistic? It is the combination of a dominant limbic system (Drive faster! Push the limits!) and a relatively quiet prefrontal cortex in the young driver.

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Raising the gun age needn’t interfere with hunting or recreational shooting by young people. So long as people younger than 25 are under the active supervision of adults of age, their possession of a firearm should remain lawful.

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The National Rifle Association, which has unsuccessfully tried to have the age restriction on purchasing handguns (the buyer has to be at least 21) struck down, would undoubtedly object to our proposal. We trust young people serving in the armed forces to have guns, the NRA might say, so why not ordinary civilians? The difference is that, in the military, these young people are closely supervised; their possession of firearms occurs within the confines of a heavily structured hierarchy that limits the opportunities for poor decision-making.

We limit other rights, including the right to vote, the right to serve on a jury and the right to marry, on the basis of age. Although 18 is a common cutoff, there’s nothing magical about that number. For guns, the science and evidence suggest, the right age is 25.