State lawmakers in Missouri last week revived an effort to significantly curtail local planners’ ability to adopt the type of smart-growth policies long touted by urban developers, demographers, and climate scientists. The bill, which sailed through the state’s lower chamber this past Monday, represents the latest victory for a onetime fringe movement that has spent the past two decades slowly gaining traction among conservatives by warning of an actual, real-life U.N.-orchestrated global takeover.

The specific target of the Missouri legislation may be well-known to heavy consumers of conservative media, but most Americans have probably never heard of it: Agenda 21, a nonbinding resolution that was signed by President George H.W. Bush and 177 other world leaders at the end of the United Nations’ 1992 Earth Summit in Rio de Janeiro. The effort was hailed at the time as an important, albeit voluntary, action plan to promote sustainable development in the face of a rapidly expanding global population, but ultimately failed to become much more than a feel-good Democratic talking point back in the United States. In 2012 a full 85 percent of Americans didn’t know enough about the U.N. resolution to have an opinion on it, according to a poll commissioned by the American Planning Association that summer.

Not everyone forgot about it, however. Agenda 21 remained front and center for a subset of right-wing conservatives who warned that it was a harbinger of a looming new world order that would culminate with the seizure of land and guns, and an end to the American way of life. If that last part sounds like the plot of a dystopian novel written by Glenn Beck, well, that’s because it is.

But what began as a far-fetched conspiracy theory has since transformed into an effective, almost methodical movement to block the type of “livability” initiatives that President Obama and his allies have made a priority. If you look past the black helicopters in the anti-Agenda 21 origin story, you’ll find a series of smart-growth-blocking victories at the state and local levels in nearly every corner of the country. The movement, fueled largely by groups like the John Birch Society and the American Policy Center, has found mounting success by targeting sustainable development efforts on multiple levels, from the individual projects themselves to the state policies that make them possible.

Local activists waving the AgEnder (their word) flag have derailed a congestion-easing highway project in Maine, a regional transportation plan in Greater Atlanta, and a high-speed train project in Florida, while causing similar trouble for a variety of other sprawl-curbing, energy-conserving projects around the country. The effort’s crowning achievements to date arguably both occurred in Alabama, where the Republican governor became the first to sign binding anti-Agenda 21 legislation into law in 2012, and where an entire nine-person planning commission in Baldwin County quit that same year in protest over the decision to scrap their award-winning regional development plan after it was tarred by its opponents. (For a more complete account of the Baldwin fight, check out the final chapter in this April report from the Southern Poverty Law Center, which also identifies some of the loudest voices in the national movement.)

Where there are no sustainable-development projects to target specifically, anti-21 activists have taken aim at the process behind such projects, working to dismantle the planning infrastructure that is needed to develop plans for smart meters, new bike lanes, or any other effort that makes curbing greenhouse gas emissions a priority. Under pressure from AgEnders, more than a dozen cities, towns, and counties have ended their relationship with ICLEI USA, a Northern California-based nonprofit that consults on sustainability issues by offering software and advice to member communities looking to go green. As the New York Times reported in 2012, the debate at a council meeting in Missoula, Mont., about the city’s four-figure contract with the nonprofit grew so heated that the police had to be called in to keep the peace.

Over the past three years, conservatives have introduced anti-Agenda 21 bills or nonbinding resolutions in a total of 26 states, passing such efforts in five of them, according to data compiled by Karen Trapenberg Frick, a policy professor at the University of California–Berkeley who has tracked the effort.*

One of the remarkable things about the campaign is that the anti-Agenda 21 activists often win simply by showing up. Frick’s research suggests that state bills—even when they fail—ultimately “inspire imitation and create momentum” for the movement, resulting in more converts around the country. Frick says she’s also noticed a relatively recent change in how activists are delivering their pitch at planning meetings: “Some activists—certainly not all, but some—are starting to shape-shift a bit to speak the language of city planners,” she told me.

Policy experts likewise see a potential “chilling effect” on future sustainability activities anywhere anti-Agenda 21 nonbinding resolutions are passed. Planners, meanwhile, will be more directly handcuffed in those states where the anti-21 efforts become law. As Dennis Murphey, the chief environmental officer for the city of Kansas City, Mo., warned last month, the Missouri bill could prevent his city from teaming with any organization that has goals in common with the U.N. resolution, which in addition to promoting sustainable development also seeks to curb global poverty and get more women involved in government. Under that strict legislative reading, the city could be forced to cut ties with everyone from the Kiwanis Club to the Girl Scouts.

While not the first to raise the anti-Agenda 21 flag, Glenn Beck has probably drawn the most attention to it. He repeatedly used his perch on Fox News early in the decade to warn of an impending one-world order. His magazine, the Blaze, put Agenda 21 on the cover of its January/February 2012 issue, calling the resolution a “global scheme that has the potential to wipe out freedoms of all U.S. citizens.” That fall he released the aforementioned science fiction novel titled Agenda 21, which tells the tale of a country “once known as America” where citizens are “confined to ubiquitous concrete living spaces” and food, water, and energy are strictly rationed. Those fears were quickly echoed by Beck’s fellow conservative rabble-rousers. Fox News’ Eric Bolling, for one, warned on air that the U.N. effort would one day lead to a world where “a centralized planning agency would be responsible for oversight into all areas of our lives.”

The hyperbolic nature of that rhetoric quickly seeped into state legislatures around the country. Two years ago Georgia Senate Majority Leader Chip Rogers used a closed-door briefing—video of which was later obtained by Mother Jones—to warn his Republican colleagues that Obama and his allies were relying on a “mind-control technique” to ensure that the plan for a totalitarian environmental government would proceed as planned. State Rep. Mike Moon, the lead sponsor of the bill now winding its way through the Missouri legislature, picked up the baton earlier this year, assuring his fellow lawmakers at a hearing that one of Agenda 21’s goals was to “elevate nature above man.”

With the exception of occasional mentions by national figures like Ted Cruz and Newt Gingrich, the U.N. conspiracy theory has largely proved a few notches too extreme to find a foothold inside the Beltway, although it did earn a mostly overlooked mention in the 2012 Republican National Committee platform, which decried Agenda 21 as “erosive of American sovereignty.”

But given the remarkable success the effort continues to find at the state and local levels, it’s evident that the AgEnder movement doesn’t necessarily need to find a seat at the table in Washington. Its current strategy would appear to be going perfectly to plan.

*Correction, May 5, 2014: This piece originally misspelled the University of California–Berekely. (Return.)