When Dwayne Dixon heard that Ku Klux Klan demonstrators were preparing to march through downtown Durham, North Carolina, on August 18, he grabbed his semiautomatic rifle and set off to join a group of counter protesters. Not a week earlier, and less than 200 miles away, hundreds of white-nationalists and anti-racist protesters had clashed on the streets of Charlottesville, Virginia, in a march that involved a multitude of weapons, unregulated armed militias, and ultimately, a murdered bystander. Dixon wanted to be prepared to defend himself and others from the anticipated swarm of newly emboldened white supremacists said to be descending on his North Carolina city.

The KKK marchers never showed up in Durham — the rally had been a rumor — and the day ended without any of the violence wrought in Virginia. It did not end uneventfully for Dixon, however: He was arrested by sheriff’s deputies, and disarmed at the scene.

The issue before local governments in the wake of the “summer of hate” is simply this: Can law enforcement intervene against the guns carried as part of a march or a protest in public spaces before bullets are fired, or only after? A lawsuit filed just last week in Charlottesville addresses part of that problem, arguing that private militias break the law when they usurp the role of the police and national guard. But what about individuals choosing to open carry in jurisdictions and circumstances where that behavior is permitted, and they claim to be merely exercising their First Amendment rights? As militant ideologies normalize, and communities lose faith that the police can protect them, an open question in open carry jurisdictions is whether gun carrying can be considered a threat before anyone gets hurt.

Laws long enshrined in North Carolina and several other states hold that the answer is “yes,” at least when certain conditions are met. It was one of those laws that sheriff’s deputies in Durham used to take Dixon, the armed leftist counter-protester, off the streets last August. In addition to breaking a state law that bans guns at demonstrations, Dixon was charged with a second crime, called “going armed to the terror of the public.” The language sounds fusty because it is: It comes from a centuries-old English statute that predates the American Revolution. In North Carolina, officers and prosecutors are finding plenty of modern-day applications for the law, bringing charges for “going armed to the terror of the public” 344 times last year.

The 14th century “Statute of Northampton,” as it was known, explicitly forbade publicly carrying pistols and daggers — whether “secretly” or in the “open” … “to the terrour of all people professing to travel and live peaceably.”  The prohibition migrated to the American colonies, such that, for instance, Massachusetts passed a law modeled on the Statute of Northampton barring residents from going out to “ride or go armed offensively, to the fear or terror of the good citizens of this Commonwealth.”

Several other American states imported the concept into their laws. Along with North Carolina, Tennessee, Alabama, and Virginia adopted versions of the ban on intimidating gun carrying. Others, like Connecticut and New Jersey, incorporated the prohibition in their manuals for justices of the peace. By the middle of the 19th century, at least 17 states had adopted laws against weapons carrying that looked very much like North Carolina’s “going armed to the terror of the public” law. Even the gun rights stronghold of Texas makes it a crime to carry a firearm in public “in a manner calculated to alarm.”

Constraints on “going armed to the terror of the public” are among the many valid boundaries that local governments have placed on the right to bear arms, which the late Justice Scalia held was not “unlimited” in his majority opinion in the Heller case.

Saul Cornell, a legal historian, distilled the idea behind this specific form of firearms restrictions when he wrote: “The liberty interest associated with the right to arms was always balanced against the concept of the peace.”

As the gun rights contingency pushes for more gun carrying in more public places, concerns for public peace are again taking shape as a compelling governmental consideration — especially now that we’re seeing those expansive public carry rights layered with a zeal for armed protest. In politically turbulent times, cities from San Francisco to Knoxville to Kansas City, Missouri are giving this historic reverence for public safety new relevance by choosing to ban guns at rallies. Far away from the police cordons, long-standing prohibitions against having your gun frighten the devil out of your neighbors have also been invoked to keep sensitive spaces gun-free. Last spring, as gun owners tried (for now in vain) to get the Supreme Court to hear their challenge to California’s concealed-carry permit system, lawyers working on behalf of Everytown for Gun Safety filed an amicus brief in which they raised “going armed to the terror of the public” laws as an example of our nation’s historic regulation of guns for the purpose of public safety. (Everytown provides funding to The Trace.)

In North Carolina, the arrests at the August 18 phantom Klan cavalcade show police deploying the law specifically to rein in armed protest. Along with Dixon, sheriff deputies sought warrants for the same violation against four others who also brought guns to the streets of Durham that day.

Dixon himself believed he was lawfully carrying openly in accordance with North Carolina’s laws, a theme that repeats itself often on Second Amendment websites. But police had received complaints from passersby who were scared by the sight of the armed protestors and the weaponry they possessed — and those public concerns, in the eyes of law enforcement, superseded the armed men’s open carry rights. Dixon’s arrest warrant noted that he was “armed with a semiautomatic weapon rifle capable of firing multiple shots within seconds, which upon observance by members of the public caused alarm and concerns for safety.”

Police officers in Fayetteville, North Carolina, also turned to the law when responding to a more benign situation in 2015. A Fort Bragg soldier had gone to a shopping mall to be photographed, in full Army garb and carrying his assault rifle. Bystanders called 911 to report the sight, and officers swept the mall. Observing that the soldier was indeed armed, in public, and to the perturbation of fellow shoppers, the police levied the “going armed to the terror of the public” charge.

Which is precisely the tool that such were intended to provide to public safety agencies. In a case dating back to 1968, the North Carolina Supreme Court cautioned rather presciently:

“In this day of social upheaval one can perceive only dimly the tragic consequences to the people if either night riders or daytime demonstrators, fanatically convinced of the righteousness of their cause, could legally arm themselves, mass, go abroad, and display their weapons for the purpose of imposing their will upon the people by terror. Such weapons – unconcealed and “ready to be used on every outbreak of ungovernable passion” – would endanger the whole community. The wisdom of the common law, which made it a crime to go armed to the terror of the people, inures to our benefit today.”

Jeff Welty is a firearms expert at the University of North Carolina School of Government who has studied “going armed to the terror of the public” laws. “They are meant to address the situation where someone is out, with a firearm, menacing people, and he hasn’t yet committed whatever crime he may commit,” he says, “but we still want to be able to check him before he gets to that point.” The laws open the door to police intervention at the sight of worrisome gun carry, without compelling officers to wait until a shot is fired.

In open-carry states without such statutes, officers can’t intervene, with potentially fatal consequences. In Colorado Springs two years ago, residents called 911 to report a man walking around with a semiautomatic AR-15 rifle. A dispatcher told a woman, “Well, it is an open carry state, so he can have a weapon with him or walking around with it.” The gun carrier went on a shooting spree later that day, killing three people.

There are objections to enforcement of “going armed to the terror of the public,” to be sure. The law is vague and turns on the subjective fear of bystanders. In online forums, North Carolina gun owners complain that the nebulous prohibition is a slippery slope to complete nullification of open carry rights: “Is it legal to open carry in NC, or just legal until someone decides they don’t like it, or what???” asked one.

But public terror at armed displays of potentially lethal force by non-governmental entities is rational, and laws that bar people from terrorizing strangers are hardly radical. Rather, they allow for a reasonable and valuable balancing between the interests of gun owners in striding around in public spaces while showing off their guns, on the one hand, and the public’s interest in not having their faces scared off, on the other. Affording bystanders the opportunity to register terror, and putting gun owners on notice that they may be engendering fear — even if they believe that parading around while armed is inherently peaceful behavior – is an important recalibration of the fundamentalist idea that all guns can be carried by anyone at any time, without causing anxiety. What was true of 14th century English hand cannons and their owners is true of black rifles and their bearers today: When gun rights bump up against the public peace, governments have consistently regulated them.

Local officials — especially in small southern cities with Confederate monuments, but without large police forces – are wondering how to turn the temperature down at rallies so as to prevent the next “Charlottesville.” Terry McAuliffe, the governor of Virginia, has assembled a task force on civil unrest to come up with some solutions that will keep protesters and counter protesters safely separated, and, more urgently, determine how to keep guns out of the hands of everyone at what is intended to be a peaceable First Amendment event, without running afoul of the courts.

As they twist themselves into pretzels to imagine a basis for keeping firearms away from powder-keg gatherings, cities and states with historic regulations on “going armed to the terror” and other laws like them may find themselves turning to yellowed books to help deal with today’s political violence. “It’s not so farfetched,” says Adam Winkler, author of Gunfight: The Battle Over the Right to Bear Arms in America and a Second Amendment scholar. “Part of that is because these laws are so grounded in history. As long as people have been able to carry guns in public, there have been concerns about them terrorizing people.”

Once you begin to regulate guns used as part of a protest or rally, you inch into complicated territory: Where does speech end and threats of terror begin? This is the very question extreme open-carry proponents, who begin with the presumption that there’s no reason to be afraid of guns, have asked state governments to assume away. But guns that escalate tempers — and risks — at protests are now forcing the issue, and courts are well equipped to determine when lawful gun carrying slides into threatening conduct.

For example, there were some militia members in Charlottesville who stood with their military-style rifles out of the fray, without incident. But there were also white nationalists in Charlottesville who shouted racial epithets and surrounded a synagogue threatening to burn it down, and for them, displaying a gun could cross the line from permitted open carry into causing acute fear. “Armed to the terror” laws allow us to litigate those vital distinctions. Adam Skaggs, who serves as chief counsel at the Law Center to Prevent Gun Violence, notes that the meaning of “armed to the terror” laws has become a central facet of current court cases on public gun carry. “Pro-regulation advocates maintain that it just refers to going armed visibly, which has the natural effect of terrorizing the public,” he says. “Pro-gun rights advocates say, no, it only prohibits carrying arms with an intent to terrorize. I’d argue that at least some protesters in Charlottesville would meet either definition.”

In other words, such regulations allow for the notion that you can open carry peaceably, but not for the proposition that you can open carry in a manner or moment that leaves people afraid of violence. Drawing that line means finally rejecting the fatuous framing of gun rights under the Second Amendment urged by hardline adherents: Our freedoms are unbounded. You must compromise around us. When applied to armed protests, that mindset takes our country to a dangerous place: The Second Amendment and state open-carry laws cannot trammel the free speech rights of unarmed protesters and the necessity for law enforcement to keep the peace. Nor should it take the breakout of actual violence for police to intervene.

As North Carolina’s quirky enforcement of its ban on armed terror shows, protections for the individual can be checked when they infringe on the rights of the members of the public, who should not be afraid to walk on their own streets.

Dahlia Lithwick writes about the courts and the law for Slate. Olivia Li, a former Trace editorial fellow, is a student at Columbia Law School.