A decade ago, such incidents still occurred rarely enough that onlookers could be surprised and upset by them. But the presence of a president did at least ensure that the preponderance of firepower lay with the lawful authorities.

Not so a decade later.

In June, a rumor spread via Facebook that protesters planned to rally at a park in Houston, Texas, to demand the removal of a statue of Sam Houston. Hundreds of supporters of the statue rallied; a large number of them carrying rifles, some wearing body armor.

Hermann park, the site of the statue, is one of the city’s most visited parks. The Houston Zoo is located within it; the Houston Children’s Museum stands just a few blocks away. On weekends, the park is typically crowded with young families. Yet some dozens of Texans decided that this would be an appropriate place to plan a gunfight. And of course they were entirely within their rights, as those rights are understood in 21st-century America. Texas law forbids citizens to carry deadly weapons “in a manner calculated to alarm.” Otherwise, long arms may be shouldered by virtually anyone in almost any place. It might be thought that bringing a rifle into a playground is itself “calculated to alarm.” But over the past generation, gun carriers have become much more assertive—and the authorities much more accommodating.

Charlottesville, however, marks a new era of even bolder assertion of the right to threaten violence for political purposes. Gun carriers at the so-called “Unite the Right” rally acted more like a paramilitary force than as individual demonstrators. They wore similar pseudo-military outfits, including body armor. They took tactical formations to surround the site of the expected confrontation. According to Virginia Governor Terry McAuliffe, “They had better equipment than our state police had.” (The state police have disputed that claim.)

The carrying of firearms by random citizens into public places is typically defended as a contribution to public safety. If criminals must reckon with the possibility of armed resistance, they will hesitate to commit crimes—or so goes the theory. It’s a hard theory to prove or disprove, because the thing to be measured—“defensive gun use”—is so subjective. An altercation erupts after a traffic accident. One motorist raises his voice. The other displays a weapon. Has the weapon carrier prevented a crime? Or has the law empowered a subset of Americans to intimidate their neighbors? The Florida man who shot 17-year-old Jordan Davis dead for playing his music too loud also claimed he was acting in self-defense. If widespread gun carry enhances safety, why are countries that forbid it so much safer than the United States?

Whatever its merits, however, the theory of the crime-reducing effects of citizen carry applies only to concealed carry. Society receives the putative benefit of citizen carry only if the potential criminal does not know which potential victim might be armed.