Maryland has one of the most far-reaching gun bans in the country. The state bans typical semiautomatic rifles that are commonly owned by millions of Americans and labels them as “assault weapons,” a meaningless term intentionally created to demonize rifles commonly used for sport and self-defense.

In Kolbe v. Hogan, the Fourth Circuit convened en banc (meaning more judges hear the case than the typical three-judge panel) to uphold Maryland’s drastic ban by applying a novel test that contradicts the Supreme Court’s decision in Heller. The Kolbe decision held that firearms that are “useful in military service” are outside the scope of the Second Amendment, which would exclude nearly every commonly owned firearm.

Mr. Bianchi and his co-plaintiffs are law-abiding citizens who would like to own standard semiautomatic rifles for self-defense, hunting, and community protection. Since colonial times, Americans have used versatile long guns for the same purposes. These multi-purpose long guns were also used in militia service and were afforded constitutional protection. Under the approach used by the Fourth Circuit, however, a state government could have banned all those weapons.

Now on petition to the Supreme Court, Cato has joined various professors of the Second Amendment, the John Locke Foundation, the Independence Institute, and the Center to Keep and Bear Arms on brief supporting Bianchi’s case. We argue that the Second Amendment and the Heller decision protects arms that are commonly owned for sport and self-defense. Standard semiautomatic rifles are undoubtedly commonly owned for lawful purposes—easily in the tens of millions—and they are very rarely used in crimes. Thus, such firearms are protected by the Second Amendment, making Maryland’s ban categorically unconstitutional.

The Second Amendment presumptively protects common, bearable arms. The burden is on the government to overcome this presumption. The government can rebut this presumption by showing that the weapon is uncommon and dangerous. A weapon may not be banned unless it is both uncommon and dangerous.

Moreover, common use is not restricted to self-defense. It encompasses all lawful purposes, such as target shooting and hunting. Further, law-abiding citizens, not the courts, decide which firearms in common use are appropriate for their personal circumstances.

The Fourth Circuit’s test is contrary to the Second Amendment and the Supreme Court’s decision in Heller. Millions of Americans living in the Fourth Circuit are not enjoying their constitutional protections. We urge the Supreme Court to reinforce its precedent and bring the lower courts into conformity.