Are AR-15s military weapons, designed for inflicting maximum damage to enemy troops? Or are they part of the American civilian gun owner’s heritage, essential for both recreational shooting and self-defense?

Most of the time, the distinction is of little practical importance: these semiautomatic rifles are ubiquitous, widely available for sale in gun shops across much of America. But on Tuesday, the Fourth Circuit Court of Appeals in Richmond, Virginia, came down squarely one side of this debate, with big implications for how states regulate assault weapons. In a 10-4 decision, the federal court upheld Maryland’s 2013 assault weapons ban, finding that guns like the AR-15 are weapons of war, and thus American civilians don’t have an unfettered right to buy and own them under the Second Amendment.

The court’s decision is uniquely forceful. While every other appeals courts to consider other states’ assault weapon bans has upheld those state laws, only the Fourth Circuit has weighed in on whether there is a constitutional right to own these kinds of weapons.

“It sends a very clear message that states are free to regulate assault weapons,” said Brian Frosh, the Maryland attorney general whose office defended the law. “The 4th Circuit is the only one to address that question head-on.”

The upshot of the decision, Frosh predicted, would be that “other states can be comfortable that if they adopt similar laws they’ll be upheld by the courts.”

There’s no question that the AR-15 was created for the military. The gun was first designed by famed engineer Eugene Stoner in the late 1950s as a replacement for rifles developed during and soon after World War II. Stoner designed a “select fire” weapon that could either shoot one bullet at a time or many rounds with one sustained squeeze of the trigger. In 1959, Colt, a much larger firearms company, bought the design from Stoner’s struggling Armalite, and produced it for the military under the designation M-16. Many gun companies now make their own versions of that weapon, along with other military-style semiautomatic rifles like the AK-47 or Sig Sauer’s recent MCX. These rifles are virtually identical in functionality to the M-16, with one difference: they lack the automatic fire feature. Meaning, its owner must squeeze the trigger each time he or she fires a shot.

After a series of mass shootings committed with commercially-sold assault weapons and fears grew that gangs were using such firearms to out-gun police, President Clinton restricted their manufacture and sale. The Violent Crime Control and Law Enforcement Act of 1994, a sweeping omnibus crime bill, included a ban on assault weapons. When that ban expired in 2004, the market for such guns opened up. Demand skyrocketed during the Obama administration, especially after Democrats introduced new gun control legislation following the massacre at Sandy Hook Elementary School in Connecticut, which was carried out with an AR-style rifle made by Bushmaster.

The case decided Tuesday by the Fourth Circuit can be traced back to Sandy Hook. In 2013, Maryland and several other states passed their own laws banning the sale, transfer, or transportation of guns like the AR-15. A group of Maryland residents, who wished to buy such weapons but were prevented from doing so under the new law, sued the state and were joined by gun dealers and trade groups like the National Shooting Sports Foundation. Pro-gun groups like the NRA and more gun-friendly state governments, including Alabama and Kansas, filed briefs backing the suit. The state of Maryland defended the law, and was supported by gun-violence-prevention groups like the Brady Campaign and states like Illinois and New York.

The two sides argued over the development history, technical features, and place in American life of these assault weapons. The plaintiffs disputed the defense’s assertion that certain features, like a coiling shroud that protect a user’s hands from the heat created by shooting multiple rounds, are unique to military-style guns. In one filing, they sounded nearly contemptuous of the defense’s fixation on these design details: “Plaintiffs dispute this ‘fact’ because Defendants’ statements inaccurately imply that this is a feature unique to ‘assault weapons.’ In fact, most firearms have either an extended stock or a barrel shroud to prevent the shooter’s hand from being burned, which can occur when even a few shots are fired.”

In contrast, the defendants pointed to the AR-15 and similar weapons’ clear origins and continued marketing as guns developed for the military. The government’s lawyers pointed to gun companies’ own marketing materials. As they wrote in one filing, “Colt relies heavily on the AR-15’s military origins, features, and specifications when marketing to civilians, boasting that its rifles are ‘based on the same military standards and specifications as the United States issue Colt M16 rifle and M4 carbine.’”

The plaintiffs pointed out that there is a crucial functional difference between the guns the military uses and those sold to civilians. In their complaint, they wrote that “the critical difference is that the banned firearms are semi-automatic, rather than the fully automatic versions used by the militaries. These two distinct classes of firearms cannot be ‘essentially identical’ and yet differ completely in their most material respect.”

The court sided with the defendants, ruling that the difference between the semiautomatic and automatic versions of the weapons is “slight” and that law enforcement officers and soldiers are often advised to use the semiautomatic feature because “it is more accurate and lethal” in many situations.

In an article on how the military considers which guns to give its service members, the magazine Task and Purpose noted, “current training emphasizes semi-automatic fire in most situations.” Carefully aimed bullets are more likely to hit their designated target, which experts agree makes one shot more deadly than another.

Civilian ownership of fully automatic weapons has been strictly regulated since the passage of the National Firearms Act in 1934, and no new automatic weapons have been produced for the civilian market since 1986.

For those outside the gun world, however, that may be a distinction without much of a real-world difference. As the judges wrote in their decision, “the automatic firing of all the ammunition in a large-capacity thirty-round magazine takes about two seconds, whereas a semiautomatic rifle can empty the same magazine in as little as five seconds.” Expert shooters can discharge as many as six rounds from an AR-15 in a single second.

Another key friction point was whether the assault-style rifles subject to the Maryland ban are “commonly owned.” The landmark Heller vs District of Columbia established an individual right to own firearms affirmed the specific right to keep handguns — explicitly because that style of weapon is so popular. The Heller decision left open the possibility that legislatures could ban other types of guns that are not commonly owned. In its opinion, the Fourth Circuit said that while AR-15s and other similar rifles are owned by a small minority of all gun owners — that the large number of sales can explained, in part, because those who buy the weapons often purchase several.

The Fourth Circuit’s decision goes farther than other decisions upholding assault weapons bans. The Second Circuit Court of Appeals in New York, for example, upheld New York state’s SAFE Act — but also ruled there is some civilian right to own an AR-15, even if the government has a compelling interest in regulating these guns. The ruling by the Fourth Circuit attempted no such balancing act.

But, right now, that distinction may not matter much outside the courtroom.

“As a practical matter, there’s not very much in the way of implications for the difference in opinions,” said Frosh, the Maryland attorney general.

The immediate result of the Fourth Circuit’s decision is basically the same as the result of the Second Circuit’s earlier decision: the state laws stay the same.

But the unequivocal language in Tuesday’s opinion could provide legal cover for other states that want to follow Maryland’s example.

[Photo: Flickr user Robert Freiberger]