A crowd of protesters was squaring off against a battalion of riot police on a city boulevard as plumes of tear gas and dust clouded the afternoon light.  It could have been Hong Kong or Santiago in 2019, Minneapolis or Portland in the summer of 2020, Tehran or Shanghai in the winter of 2022.

But at this particular eruption of unrest in the spring of 2021 – in Popayán, Colombia, a small city about 250 miles southwest of Bogotá – the basic grammar of protest and retaliation was about to take a harsh new shift.

Scores of young demonstrators were crouching behind a line of homemade shields, trying to hold back the authorities. Colombia had been in the midst of a general strike for more than two weeks, triggered by a series of tax increases handed down in the middle of a debilitating Covid shutdown. But as nationwide protests escalated in tandem with the state’s response to them, police brutality became the demonstrators’ main grievance.

On the frontline that afternoon in Popayán, a 22-year-old engineering student named Sebastian Quintero Munera took cover behind a piece of plywood spray-painted with the phrase “Alison We Are With You” – referring to a local teen who had died by suicide the previous morning after alleging that she’d been sexually assaulted in police custody.

On the other side of those shields, officers in riot gear were spread out across the width of the street in groups of two. Behind them, on the tree-lined median that divided the boulevard, another group of officers huddled around an unusual box with an array of metal tubes pointing out of it, mounted on a small tripod. It looked a little like the kind of equipment used to launch fireworks in a big New Year’s pyrotechnic display. But the tubes were aimed at the street, not the sky.

Without warning, a rapid succession of deafening blasts echoed down the block. A barrage of blunt, barely visible projectiles ricocheted against the shuttered windows of second-story apartments, off trees and light posts, shields and bodies, as the street filled with a dense fog of tear gas. The effect on the crowd was almost instantaneous. Gasping for air, protesters scrambled over each other to retreat. They tripped on abandoned shields, motorcycle helmets, and other make-do armour. Within seconds, the officers reloaded the contraption and fired again.

The box on the tripod was a remote-controlled launcher called a Venom, made by the US firm Combined Systems. Long used by the US Marine Corps for combat operations in Iraq, Venom is capable of firing up to 30 tear-gas or flash-bang canisters at a time.

According to José Miguel Vivanco, who was the director of Human Rights Watch’s Americas division at the time, Colombia’s clampdown against demonstrators in 2021 marked the first time Venom had been used in Latin America, and it was one of the most brutal examples of its indiscriminate use by police against civilians anywhere in the world.

The launcher’s deployment in Colombia represented a new high-water mark for a pervasive but often overlooked industry. Venom is now marketed to militaries and police forces around the world as a top-tier “less-lethal” weapons system. Sales of such weapons have quietly grown over the past few decades and are now estimated to be a multibillion-dollar business.

Demand has inched up alongside a historic rise in economic inequality, political turmoil and mass demonstrations. According to numerous researchers, the past decade or so has seen nearly unprecedented protests worldwide, and less-lethal weapons are the chief technologies devised to contain them.

The theory behind all less-lethal crowd-control devices, from the simple billy club to the infrared laser dazzler, is that they allow security forces to suppress a riot without committing a massacre. Law enforcement and military experts have described them, again and again, as a “humane” alternative to conventional arms – and often as the frontier of high-tech innovation.

Perpetually just around the corner, it seems, is the widespread adoption of futuristic weapons like sticky foam, net guns and heat rays.

That rhetoric obscures how remarkably stagnant the main menu of less-lethal crowd-control weapons has remained. Tear gas has been around for about 100 years, rubber bullets for 50, flash-bang grenades for 45, and Tasers for 30. The language has also masked how brutal these weapons can be, and how much they’ve been neglected by oversight bodies.

Tear gas – probably the most important less-lethal weapon for crowd control – has been prohibited for use in war since the 1925 Geneva Protocol. But no international treaty bans countries from using it against their own citizens. Less-lethals are also specifically excluded from the 2013 Arms Trade Treaty, a binding agreement that prohibits the sale of weapons to countries with documented human rights abuses. And in the United States, the world’s leading producer of less-lethals, no federal legislation specifically regulates their manufacture.

Unhindered by the kind of oversight on production, sale, use, and export that applies to typical small arms, the less-lethals industry has been left pretty much to its own devices. It is to the armaments trade what dietary supplements are to the pharmaceutical industry: a supposedly more benign sector that is, in practice, largely unsupervised and often slipshod.

The effects of these weapons are not minor. Even if they are designed not to kill, the less-lethals most commonly used in crowd control – tear-gas canisters, rubber bullets, flash-bang grenades—can easily break limbs, shatter skulls, burn and lacerate skin, destroy eyesight and hearing, concuss brains, and contuse flesh.

“They are as dangerous as the person firing them wants them to be,” says physician and human rights activist Rohini Haar. And as a growing body of research shows, these weapons have left a distinct trail of injuries in the wake of movements like the Arab Spring, the Hong Kong protests of 2019, and the Black Lives Matter demonstrations of 2015 and 2020.

In the huge protests that swept Chile in 2019, ocular wounds from rubber bullets and other projectiles were so rampant that eye bandages became a nationwide symbol; the Chilean Ophthalmology Society called it the largest outbreak of such injuries ever registered in a conflict zone.

I know the impact of less-lethal weapons all too well: I was shot in the face with one while covering a protest outside the White House in 2020. And sometimes the violence these weapons do to protesters’ bodies is even more severe.

When the smoke cleared from the streets of Popayán last May, Sebastian Munera was lying on the ground with a fist-sized hole in his neck, bleeding out onto the pavement.

• A Wired report