In 1986, working as an undercover narcotics agent, Ron Stallworth bought a gram of crack cocaine from a dealer for $100. That wasn’t unusual: The country was awash in cocaine of every variety, and never mind Nancy Reagan’s exhortation to “Just say no.” What was unusual was that the buy was in Salt Lake City, the capital of the straight-laced Church of Jesus Christ of Latter-day Saints, and that the seller was a young Black man from Los Angeles, a member of the street gang turned crime syndicate called the Crips.

As Stallworth recounts in his new book, The Gangs of Zion: A Black Cop’s Crusade in Mormon Country (Legacy Lit/Hachette, Sept. 17), he wasn’t surprised to find a Crip within a rock’s throw of the Tabernacle. A decorated agent in the employ of the Utah State Police, he’d been reading reports from the Los Angeles Police Department warning municipalities that both the Crips and the Bloods—mortal enemies on their own turf but allies in expanding the drug trade outside it—were spreading out along interstate highway corridors to places like Denver, Kansas City, Phoenix, and, yes, Salt Lake City.

“What did surprise me,” Stallworth writes, “was how those reports and their warnings were being ignored by my peers. A flood was coming our way, but nothing had changed. Nobody was responding to the threat, so I had to.”

Further surprises were to come, not least the fact that within no time locals, mostly young white men looking for excitement and cash, were signing up to join the gangs. “I believe in my Mormon faith. One hundred percent,” one young man who’d been busted told Stallworth. “But I also believe in being a Crip. I’m a Crip and will always be a Crip.” Replied Stallworth, nonplussed, “Mormonism doesn’t teach drive-by shootings. Mormonism doesn’t teach throwing Molotov cocktails at your enemies’ houses. How do you reconcile the two?” He didn’t get a good reply.

Speaking with Kirkus from his home in West Texas, where, long since retired from law enforcement, he spends his days writing, Stallworth recalls his lonely battle to interdict the drug trade in Salt Lake City. “The street officers knew what was going on,” he says. “Everybody knew what was going on except the administration, which denied that there was a problem. They had their heads stuck up their butts. None of the higher-ups in Utah law enforcement paid attention to the warnings. The attitude was always, This is Utah. We’re a pure, homogenous community. We don’t have to worry about stuff like that. Religion will cover us.”

Well, as the aforementioned episode demonstrated, religion didn’t quite do the trick. The next card to play in the denial game, Stallworth says, was for the SLCPD to suppress any mention of the problem. “We were forbidden to use the word gang,” he says. “They would call them youth groups, organizations, youth organizations, or whatever. Any metaphor, but the word gang was not used.”

A born contrarian, Stallworth refused to play. “I started using gang. I openly used it, and since I was a state cop, they couldn’t stop me from saying it.”

He sent a report up the chain of command, saying that it was time to acknowledge that Salt Lake did indeed have a crack problem. He also pitched creating a task force under the aegis of the city’s police department to coordinate communication across law enforcement agencies. All the while, he kept working undercover, as he’d done for a decade and a half, first in Colorado, where the seemingly improbable events of his 2014 memoir BlacKkKlansman, turned into a film by Spike Lee four years later, took place. “I wasn’t put in narcotics because I was exceptional,” he writes in Gangs. “I was put in narcotics because they needed a Black face to penetrate Black environments.”

He then moved on to Wyoming to serve, as he puts it, as “the only Black undercover investigator in the whitest state in the country.” He soon had occasion to underscore that distinction when a clutch of cowboys repeatedly called him “boy” before selling him a gram of powder cocaine. Busted hard, the cowboys got their comeuppance. Counsels Stallworth, “The moral to this story? Never call a Black man ‘boy.’”

After three years on the job, Stallworth finally got the Salt Lake Area Gang Project going, and there he increasingly encountered the “gangs of Zion” of his title. “They did not disavow their religion,” he says. “They clearly identified themselves as Crips who happened to be Mormon. My partner was a devout Mormon. We cracked up when we first heard it—we thought it was hilarious. But we realized these kids were serious.”

One sign of that seriousness was that the young gangsters listened not to the Osmonds but to so-called gangster rap and hardcore hip-hop. Mystified at first, Stallworth began listening to the likes of Public Enemy and N.W.A., increasingly realizing that the rappers had a point: They had legitimate grievances, many of them centered on the police.

Even with the formation of the gang unit—still operative, under a different name, four decades later—police leadership and city government took predictable views. Against all evidence, they blamed the gang activity and drug trade strictly on outsiders—and then, when that didn’t work, on the city’s Pacific Islander and Latinx communities. The late Margaret Corradini, Salt Lake City’s first female mayor, went so far as to call for a ban on the sale of gangster rap records and any movies with a hint of gang activity. “I asked her if she was willing to ban the movies of John Wayne, which depict violent genocide against Native Americans,” Stallworth says. “Hell, in the first Terminator movie, Arnold Schwarzenegger kills 30 cops in the first minute. And I asked her if she was willing to ban the showing of the old Untouchables TV show, because every week they did a drive-by shooting. No? So why are you picking on movies made by and for young Black people about their society, their environment? Why are you picking on them and ignoring all this other stuff by white artists?”

Such questions didn’t make Stallworth many friends among the brass, and he was eventually reassigned to a desk job. It didn’t take, and one day, he writes, he looked around and thought, I don’t like any of you people.

He left law enforcement, but his experiences gave him plenty of material to write about. He publicly advocates against both gang violence and policing excesses, frequently speaking about the issues at conferences and to the media. “One thing I want readers to take away from my book,” he says, “is that you have to be willing to stand up for your beliefs and speak truth to power. I hope people recognize that everything that I did, I believed in. I got into trouble with my superiors at the Department of Public Safety. They didn’t want me to say certain things in public, and I politely told them to fuck off and did what I had to do. I’ve never regretted it.”

Gregory McNamee is a contributing writer.