The Second Amendment is an area of law with many open questions. The amendment itself states that “[a] well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.” In the previous article of this Second Amendment explainer series, I explored how the Supreme Court has decided who qualifies as part of “the people.”
In this article, I examine what, according to the court, comprises the category of “arms” protected by the Second Amendment. Like “the people” question, what may seem relatively straightforward turns out to be a good deal more complicated.
What exactly counts as arms?
To begin answering this question, we have to go back to the 1939 case of United States v. Miller. In Miller, the justices considered a challenge to the National Firearms Act, enacted in 1934 to regulate certain firearms, which made it illegal to transport a firearm in interstate commerce without complying with certain requirements. The defendants were charged for transporting “a double barrel 12-gauge Stevens shotgun having a barrel less than 18 inches in length” (that is, a sawed-off shotgun). They challenged the prosecution on Second Amendment grounds and won at the trial court. (Although when the case was appealed to the Supreme Court, the defendants did not submit a brief or show up to oral argument.)
The court sided with the state. In its view, the Second Amendment was not an individual right, but connected to service in the militia and thus only protected possession of those instruments which had “some reasonable relationship to the preservation or efficiency of a well regulated militia.” In other words, to come under Second Amendment protection there must be evidence that a weapon is part of “ordinary military equipment, or that its use could contribute to the common defense.” The court went on to explain that members of militias were typically expected to supply their own arms which would be “of the kind in common use at the time.” And given no evidence that a sawed-off a shotgun had any meaningful militia usage, the court held that this did not come within the Second Amendment’s protection.
For almost 70 years after Miller was decided, the Second Amendment was rarely invoked by courts. Lower courts understood Miller to hold that the right applies “only to individuals enrolled in military organizations” – and because very few firearm regulations over individuals implicate state militias, those pushing for more expansive firearms rights in court met with little success.
This changed dramatically when, in 2008, the Supreme Court decided District of Columbia v. Heller, and recognized a personal right to own a handgun. Relying on Miller, the majority explained that the militia was typically comprised of men who brought their own weapons, which were “arms ‘in common use at the time’ for lawful purposes like self-defense.” Unlike in Miller however, the Heller majority found that the Second Amendment confers an individual right to own a firearm and rejected the idea “that only those weapons useful in warfare [or militia service] are protected.” Rather, “the Second Amendment extends, prima facie, to all instruments that constitute bearable arms,” and “even those that were not in existence at the time of the founding.” Ultimately, the majority struck down the D.C. handgun ban at issue because the handgun is the “quintessential self-defense weapon” and therefore “a complete prohibition of [its] use is invalid.”
At the same time, again echoing Miller, the court recognized that the Second Amendment does not “protect those weapons not typically possessed by law-abiding citizens for lawful purposes, such as short-barreled shotguns” (and perhaps “M-16 rifles and the like”). This was because, as the majority in Heller explained, there was a “historical tradition of prohibiting the carrying of ‘dangerous and unusual weapons.’”
The issue of “arms” arose again in the 2016 case of Caetano v. Massachusetts, which challenged a Massachusetts law that prohibited the possession of stun guns. In a per curiam opinion, the justices vacated a decision of the Supreme Judicial Court of Massachusetts which held that stun guns were not protected by the Second Amendment. Specifically, the court rejected the Massachusetts court’s conclusion that because stun guns were not “the type of weapon contemplated by Congress in 1789 as being protected by the Second Amendment” nor are they “readily adaptable to use in the military,” such weapons could be banned. The court’s two-page opinion did not provide much affirmative guidance on the proper way to go about an analysis. But it did reaffirm two ideas from Heller. First, that the Second Amendment protects some arms that were not in existence at the time of the Founding and, second, that the right is not necessarily coextensive with weapons that are useful in military service.
Based on this precedent, two categories of weaponry have produced an especially significant amount of litigation: (1) semiautomatic rifles, and (2) large capacity magazines.
Semiautomatic rifles
The right to have semiautomatic rifles (such as the AR-15) is one of the most prominent Second Amendment issues still to be decided by the court. A semiautomatic rifle is a type of firearm which fires a bullet “each time the trigger is pulled, automatically ejecting the spent casing and reloading a new round.” So far, no federal court of appeals has struck down a state ban on these types of arms, although a few district courts have done so (and some of those cases are waiting to be decided by the appellate courts). Currently, there are at least two petitions pending before the Supreme Court on this issue: Viramontes v. Cook County and National Association for Gun Rights v. Lamont.
One of the courts to consider whether these weapons come within the Second Amendment’s meaning of arms was the United States Court of Appeals for the 4th Circuit when it decided the 2024 case of Bianchi v. Brown. This case, decided by the full court, considered a challenge to a Maryland law which functioned as a ban on “assault weapons,” there defined as “(1) an assault long gun; (2) an assault pistol; or (3) a copycat weapon,” capable of “semiautomatic fire.” The majority concluded that the types of firearms at issue “fall outside the ambit of protection because, in essence, they are military-style weapons designed for sustained combat operations that are ill-suited and disproportionate to the need for self-defense.”
The majority pointed to two aspects of Heller to support this conclusion. First, the court highlighted language from Heller which said “that the sorts of weapons protected [by the Second Amendment] were those ‘in common use at the time,’” and “that [this] limitation is fairly supported by the historical tradition of prohibiting the carrying of ‘dangerous and unusual weapons.’”
Second, the court pointed to the fact that Heller declared “self-defense” to be “the central component” of the individual right conferred by the Second Amendment. This meant, according to the 4th Circuit, that the right is about empowering individuals to protect themselves when the government is unable to do so. But semi-automatic rifles “inflict[ed] damage on a scale or in a manner disproportionate to the end of personal protection.”
The dissent – which explicitly invoked an originalist understanding of the Second Amendment – came to the opposite conclusion. This was based on a definition of arms drawn from Founding-era dictionaries, which “refers to all ‘weapons of offense, or armour of defence’ or ‘any thing that a man wears for his defence, or takes into his hands, or useth in wrath to cast at or strike another.’” In the dissent’s view, because semiautomatic rifles “can be borne and used to harm others,” they qualify as arms. The dissent then turned to the dangerous and unusual inquiry. Here, the burden was on the government to show that semiautomatic rifles are not typically owned and used by “law-abiding citizens for lawful purposes” and that these types of firearms are “particularly useful for criminal activity.” Because semiautomatic rifles are quite popular and owned by a large number of Americans, the dissent argued that they cannot be banned consistent with the constitution.
Slightly over a year ago, the court declined to take up this case. Justices Clarence Thomas, Samuel Alito, and Neil Gorsuch all indicated that they would have done so. Justice Brett Kavanaugh did not vote to grant review but wrote a short statement concerning the denial. In his statement, Kavanaugh explained that he was not convinced the 4th Circuit’s decision was correct but that the issue was not yet ripe for the Supreme Court to get involved since other circuit courts were presently deciding similar cases. Kavanaugh nevertheless stated that the court “should and presumably will” address the issue soon, “in the next Term or two.”
Large-capacity magazines
Another category of cases that implicate the question of arms involve challenges to laws that ban large-capacity magazines. This classification typically encompasses any magazine that holds more than 10 rounds of ammunition. As with semiautomatic rifles, it has been argued that LCMs do not constitute arms. Some federal courts of appeals and state supreme courts have agreed with this argument. Other courts have found (or assumed) that LCMs are arms, but upheld the challenged regulations because there was a sufficient historical tradition justifying barring them.
In the 2023 case of Barnett v. Raoul, for example, Illinois attempted to defend its prohibition on LCMs by arguing these were not arms and could therefore be banned without violating the Second Amendment. The United States Court of Appeals for the 7th Circuit agreed, explaining that it read Heller to define arms as those “weapons in common use for a lawful purpose” because they protect an individual’s right to self-defense and not those “weapons that may be reserved for military use.” Because LCMs are supposedly more similar to machineguns than they are to a firearm individuals would typically use for self-defense, the 7th Circuit denied that they were among the arms that enjoy constitutional protection.
In the 2024 case of Hanson v. District of Columbia, the United States Court of Appeals for the District of Columbia Circuit considered a similar challenge to a Washington, D.C. law banning LCMs. To frame its analysis, the court laid out two questions: Do LCMs “constitute bearable arms?” And if they do, are they “‘in common use’ for a lawful purpose, such as self-defense?” The court found that the answer to the first question is likely yes because “[a] magazine is necessary to make meaningful an individual’s right to carry a handgun for self-defense” and if it were not considered an arm, the government would be able “to sidestep the Second Amendment with a regulation prohibiting possession at the component level, ‘such as a firing pin.’”
The D.C. Circuit next turned to the common use inquiry. The court first rejected the idea that common use can be determined by simply counting how many people own a particular weapon. As the circuit court pointed out, there are far more machine guns owned by individuals than stun guns, yet the Supreme Court has said that the Second Amendment protects the latter but not the former. The D.C. Circuit then focused on the “dangerous and unusual” nature of LCMS, and in particular, their ability to “facilitate crime and, specifically, to perpetrate mass shootings.” Given this, it held that possession of such arms was not protected by the Second Amendment.
So what do we know
As with similar questions surrounding the Second Amendment, there seems to be much confusion and relatively few answers. Post-Heller, the court has made clear that there is an individual right to own handguns and that some types of weapons (such as machine guns) likely do not receive such constitutional protection. But where semi-automatic rifles and large-capacity magazines fit into this picture are unclear. And this will remain the case until the justices step in, which, at least according to Kavanaugh, may be sooner rather than later.
