In an airy Denver café populated almost entirely by young people staring at laptops, Travis Tyler Fluck—dressed in an orange velour jacket, over which is draped a thin braided lock of hair—takes out his phone and pulls up Craigslist. A quick search lands him on a post advertising $10 magic mushrooms, with a poorly lit photo of said mushrooms. A good deal for anyone but Fluck, who helped lead the ballot campaign to essentially decriminalize magic mushrooms in this city by making enforcement an extremely low priority, a measure that passed by the slimmest of margins early last month.

Instead of reaching out to the seller, he flags the post. After all, the measure says you can grow and possess mushrooms for personal use, but that doesn’t mean you can sell them. Selling on Craigslist is a bad look for a measure that a small majority of voters approved.

Kevin Matthews—director of Decriminalize Denver, which led the ballot campaign—arrives and sits down on a couch opposite Fluck, who shows him the post on his screen.

“Good,” says Kevin, who has used mushrooms, aka psilocybin, to treat his depression. “Have you noticed an uptick?”

“No,” Travis says. “I think there might be other people doing the same thing I'm doing and flagging them. We were like, Oh we should totally follow up with them and meet them. But I don't have time for that.”

Matt Simon covers cannabis, robots, and climate science for WIRED.

Welcome to a murky new front in the war to bring psychedelics out of the shadows and into both legal recreational use and professional drug-assisted therapy. In recent years researchers have shown that psychedelics like mushrooms and LSD appear to treat a range of disorders, including depression and PTSD. The paradigm is so promising, in fact, that the FDA has granted MDMA breakthrough status in phase 3 trials, thus fast-tracking the approval process. Psilocybin itself is undergoing two separate clinical trials.

Meanwhile, the psilocybin decriminalization movement is snowballing at an incredible clip. Last week, the Oakland, California, city council voted unanimously to decriminalize a range of psychedelic plants, including mushrooms and cacti. And Oregon is considering a measure in 2020 to allow access to “guided psilocybin services,” while lowering penalties for possession.

The concern, as Michael Pollan—author of How to Change Your Mind, a recent book on psychedelic science—expressed in a piece in The New York Times last month, is this: The accelerating movement to decriminalize psilocybin risks a political backlash, which could derail that promising research. “It would be a shame if the public is pushed to make premature decisions about psychedelics before the researchers have completed their work,” he writes.

Taking too much psilocybin won’t kill you, but you can certainly overdo it and put yourself in danger. And we need far more research on how psychedelics might affect different individuals, especially those with serious conditions like schizophrenia.

How quickly is the push to decriminalize psilocybin progressing, exactly? So quickly that it’s even surprised psychedelics advocates. “The fact that it's happening so fast is kind of amazing,” says Brad Burge, spokesperson for the Multidisciplinary Association for Psychedelic Studies (MAPS), which leads studies of psychedelic therapies, including the aforementioned MDMA trial. “Here we have some of the very first policy measures ever to be proposed around the decriminalization of psychedelic substances and they're passing. This is so surprising, I've only just had a chance to start thinking about it.”

MAPS wants to realize the legalization of psychedelics for adult use. But it’s not so simple as legalizing and calling it a day.

“While it's definitely exciting, we also want to make sure there are notes of caution and there's adequate public education around the risks,” says Burge. When MAPS does psychedelic studies, the patient is under the constant supervision of therapists, who talk the subject through the experience. They’re free to move at their own pace and talk about past traumas, for instance. It’s a safe, comfortable, highly moderated space for a journey that can be jarring. Out in the wild, that experience may be harder to control.