In December 2012, when Washington’s press corps was peering over the “fiscal cliff,” Oklahoma Sen. Tom Coburn released a report that looked and sounded too goofy to be real. The cover of “Safety at Any Price: Assessing the Impact of Homeland Security Spending on U.S. Cities” portrayed a child-size drone flying near the Capitol; over ATV-driving Lego men; and, for some reason, over R2D2.

“If in the days after 9/11 lawmakers were able to cast their gaze forward ten years,” wrote Coburn, “I imagine they would be surprised to see how a counter-terrorism initiative aimed at protecting our largest cities has transformed into another parochial grant program.”

His researchers had dug up dozens of examples and told the story of how local police forces started to look like occupying armies, thanks to $35 billion in Department of Homeland Security grants. Seattle had spent $80,000 on a drone, which it insisted was not a drone. Pittsburgh had spent $90,000 on a sonic cannon, and used it to break up G-20 protests, though a SWAT officer assured a reporter that the device was just “a speaker that delivers an intended message to an intended group of people to disperse.”

And then there were the armored vehicles. Police departments in less-than-bustling towns suddenly needed $250,000 armored BearCats. “Because Fontana, California considers itself a ‘top 100 terrorist target,’ ” wrote Coburn’s researchers, “it needed a BearCat.” In New Hampshire, the libertarians of Keene had been fighting, unsuccessfully, a police department that wanted a BearCat to guard an annual harvest celebration. “Do I think al-Qaida is going to target Pumpkin Fest?” Keene’s police chief asked, rhetorically. “No, but are there fringe groups that want to make a statement? Yes.”

There were no attacks, and there was little coverage of Coburn’s report. Gene Healy, a vice president of the libertarian Cato Institute, publicized Coburn’s findings in a column. Radley Balko, a former Huffington Post reporter who’d worked with Healy at Cato (and, full disclosure, with me at Reason), praised the report, which touched on stories he’d covered, like the BearCat fight in Keene. Coburn appeared on Neil Cavuto’s Fox Business show (not to be confused with the more widely watched Fox News shows), where the discussion quickly veered from the report’s highlights (“zombie apocalypse training”) to the more exciting fiscal cliff. Attacking the military buildup of local police, on its own, was just too kooky.

What a difference Ferguson makes. This week, when Sen. Rand Paul published a brief op-ed denouncing “Washington has incentivized the militarization of local police precincts by using federal dollars,” he conquered the headlines. The New York Times, which had just published an epic story about libertarians, offered that “conservatives tend to be fairly consistent” on law and order, and Paul was acting as a disrupter. “Rand Paul is right,” argued Al Sharpton, who is more familiar with being labeled an “outside agitator” by conservatives than with complimenting them.

But libertarians and libertarian-leaning Republicans have been attacking the militarization of police forces for the better part of a decade. They come at the issue from a stronger ideological position than the left does, or can. Decades of tough-on-crime policies have made the right (and libertarians are part of the right) less vulnerable to charges of softness and thug-coddling. And the libertarian answer to crime has never been about empowering the police. In the ideal liberal scenario—call it “Japan” or “any part of Europe”— civilians have as much access to firearms as they have to rocket launchers and ICBMs. In the libertarian ideal, the state has no more firepower to control civilians than the civilians have to police themselves, or to fight back.

It’s hard to date when the backlash began, or when it became mainstream, but 1989 is a good time to start. That was a hot year for the crack wars, not long before Washington Mayor Marion Barry was arrested with a pipe in the room, and the year Congress’ National Defense Authorization Act added Section 1208. The new NDAA language authorized the transfer of excess military equipment “suitable for use” in “counter-drug activities.”

In 1989, that meant almost anything. The first time many Americans realized that was in August 1992, when the ATF, FBI, Border Patrol, U.S. Marshals, Idaho National Guard, Idaho state police, and local police laid siege to Randy Weaver’s home in Ruby Ridge, Idaho, with assault weapons and night-vision goggles. The siege started with the deaths of Weaver’s son and one of the dogs, and the Weaver family would eventually settle for more than $3 million. But less than a year later, some of the same agencies (and some of the same agents, as Radley Balko points out in Rise of the Warrior Cop) raided David Koresh’s compound outside Waco, Texas, smashing the walls with tanks and shooting 350 rounds of tear gas inside.

Seventy-six people died. But Bill Clinton was in the White House. The gun control lobby was experiencing what would be, in retrospect, its finest hour—the passage of the Brady Handgun Violence Prevention Act and the Violent Crime Control and Law Enforcement Act, which banned the sale of “assault weapons” until 2004.

As conservatives and libertarians saw it, and as the gun lobby saw it, the government was arming a police state while making it illegal and impossible for citizens to defend themselves from tyranny. “Not too long ago, it was unthinkable for federal agents wearing Nazi bucket helmets and black storm trooper uniforms to attack law-abiding citizens,” read a 1995 National Rifle Association fundraising letter signed by Wayne LaPierre. “Not today.” You can draw a straight line from that letter to, this week, WorldNetDaily posting photos of American cops who look like they’re breaking up rallies in Tahrir Square.

After the events of this week, the right-wingers who’d been warning about fat contracts arming thuggish police departments are suddenly finding themselves in step with the left. But it’s the right-wingers who might be the best political allies that Ferguson’s black protesters have. Like Trayvon Martin’s Florida, like John Crawford’s Ohio, Michael Brown’s Missouri is governed by a Republican legislature that has gerrymandered itself into at least another decade of power. State Sen. Maria Chappelle-Nadal, who represents Ferguson and live-tweeted her tear-gassing by police, is one of 10 Democrats outnumbered by 24 Republicans. Florida’s Dream Defenders, who occupied the state Capitol to demand a second look at “stand your ground” law, made up no ground at all with the conservative legislators.

But the Dream Defenders have common cause with libertarians. In Keene, for example, the movement to stop the BearCat sale—“tanks, but no tanks”—was led by libertarians who ideally wanted a cop-free city. Pete Eyre, who once aspired to become a police officer, became a libertarian instead, and ended up in Keene after touring the country in an RV to make movies about freedom.

“On the road, we just happened to have interactions with police employees, and it seemed clear that they didn’t like being filmed,” Eyre told me. “It became clear that capturing the truth of the situation might be powerful.”

That revelation led Eyre to co-found CopBlock, which encourages citizens to film the police—an action that got two reporters illegally arrested in Ferguson, piling outrage on top of the outrage. It also led to Eyre’s lobbying (“there were songs, music videos, petitions”) against the BearCat, which became enough of an early warning signal to make it into a Republican senator’s paper about post-9/11 police militarization.

“As people start to film what they see and pursue tactics that are peaceful,” said Eyre, “ultimately these incidents will continue to happen until the institution of policing, which is a coercive monopoly, is denied legitimacy. Badges don’t grant extra rights. If an action’s unlawful for me or you, it’s unlawful for anyone.”

That’s further than many liberals would be willing to go, obviously. And they’re not going to stop campaigning for gun control. But if they want to stop police departments from turning into shoot-first armies, the libertarians have been waiting for them. In June, 18 months after the Coburn report, the New York Times’ Matt Apuzzo published a wide-ranging study of what military equipment was making it to the sheriff’s office and how. In Morgan County, Indiana, the police acquired an MRAP because, in one sergeant’s words, “a lot of people who are coming out of the military that have the ability and knowledge to build IEDs and to defeat law-enforcement techniques.”

If that sounded familiar, it may have been because in April 2009 the DHS released a report warning that the fringe was rising and that “rightwing extremists will attempt to recruit and radicalize returning veterans in order to exploit their skills and knowledge derived from military training and combat.” This was just days before the first big national wave of Tea Party rallies, and to the horror of progressives, some activists showed up with signs that dared the DHS to go after “rightwing extremists” like them.

Five years later, the progressives still disagree with the right-wingers. They still reject, as insane, the idea that a heavily armed citizenry might be safer than a country where the cops have the guns. But they suddenly agree about something.

Read the rest of Slate’s coverage of the protests in Ferguson.