The mass shooting in Buffalo, N.Y. last Saturday has renewed the debate over the minimum age for legally purchasing what some people — such as President Biden, call "weapons of war."
An 18-year-old is accused of driving to a supermarket and targeting African Americans as he opened fire, killing 10 people. He's charged with first-degree murder in a shooting authorities describe as racially-motivated domestic terrorism.
Police say he used a semi-automatic rifle called the Bushmaster XM-15, which he bought legally at a licensed gun store, after passing a background check.
In a statement investigators believe the 18-year-old wrote and posted online, he says he modified the rifle in ways that would make it illegal under New York's definition of "assault weapons."
New York Gov. Kathy Hochul vowed Wednesday to address domestic terrorism and gun violence by establishing a new state law enforcement unit focused on domestic terrorism, among other steps.
But one question remains: Should an 18-year-old be allowed to buy a semi-automatic rifle?
In the last couple of years, California, Florida and Washington state have responded to the string of mass shootings by young men by raising the minimum age to buy certain kinds of rifles, such as the Bushmaster.
Gun rights groups, meanwhile, have sued, calling this a violation of young adults' Second Amendment rights.
Last week, a panel of three federal judges in California agreed, overturning the higher minimum age approved by the state last year.
"There's a big fight brewing over these restrictions on guns for 18, 19, and 20-year-olds because the courts are in the midst of a great expansion of Second Amendment gun rights," says Adam Winkler, a UCLA law professor who writes about gun policy.
The author of the California law, state Sen. Anthony Portantino, says he hopes the state attorney general appeals the federal ruling.
"It makes sense to appeal. This is a fight worth fighting, and again, look at what happened in Buffalo," he says. "You have to be 25 to rent a car. You have to be 21 to drink. Why would we put a semi-automatic rifle in the hands of a teenager?
Some people age 18-25 who own guns feel like it's discrimination to limit age on gun ownership
But to people in that age group who own guns, this feels like discrimination.
"I would point out that drinking and driving a car aren't constitutionally protected," says Evan Jones, a gun enthusiast in Texas who just recently turned 22.
"Eighteen to 21-year-olds, they have all the same rights and responsibilities as any other adult. And it's not fair to single out and deprive them of one right," he says.
Historically, the courts have limited such rights. "The threshold test is what's called 'strict scrutiny,' " says Jeffrey Fagan, a law professor at Columbia University who specializes in gun laws. "It's got to be a compelling governmental interest to limit the right."
For that, advocates of a higher minimum age point to brain science.
"We know from lots of studies around motor vehicles and drinking and other common types of injuries that this age group is still developing its frontal lobe, impulse control, judgment," says Megan Ranney, an emergency physician and academic dean at the School of Public Health at Brown University.
Gun rights advocates, on the other hand, say brain science arguments don't justify taking away the right to armed self-defense from a whole age group.
Matt Larosiere is with the Firearms Policy Coalition, which led the challenge to California's law. He says it's bad enough that federal law bans adults under age 21 from buying handguns from licensed dealers; he says it's worse when states bar that same age group from buying rifles and other long guns.
"States pass these 18-to-21 rifle bans, and it eliminates completely the ability of young adults of the mechanism of defending themselves," he says. And, he argues that young adults may actually rely on that right more than older people.
"There are plenty of young adults in America who are quite often lower-income, or otherwise disadvantaged, not just financially," Larosiere says. "And those are the same people who are the most likely to be violently victimized, and the people most likely in need of an effective mechanism to protect themselves,"
This legal tension has yet to be resolved. Just last year, a federal judge upheld Florida's new, age-based law limiting gun sales — but he also called this age question "a constitutional no man's land."
We may get more clarity on this from a pending Supreme Court case about gun control in New York. That case also weighs individual rights against societal risk, and if the ruling is broad enough, legal experts say it could tell us how the new conservative majority might come down on the idea of limiting gun rights by age.