When I was in London, I attended some events organized by the Psychedelic Society, a group championing the safe use of psychedelics and campaigning for their legal regulation. The society’s latest project involves a hands-on approach to advocacy for the drugs: a series of “experience weekends” in which participants take psychedelic trips as a group, by eating psilocybin-containing truffles.

In a Skype call, founder and director of the Psychedelic Society Stephen Reid, told me more: “The psychedelic experience weekends started this year. We had the first one at the end of February, and then the second one in the middle of May. We take groups of people from the U.K. to the Netherlands for an experience with psilocybin truffles, which are legal there, and the idea is that the weekends should be safe, legal, and affordable for those who want to take part.” The cost for the weekend is £300, or around US$410.

Here’s how it works: Participants meet in London on a Friday morning before taking a train to Amsterdam. From there they travel to a smaller and more secluded location outside the city, where they arrive, relax for a while, and then cook dinner as a group. This is followed by an opening circle where members of the group can discuss how they’re feeling — it’s “often a little nervous, understandably,” said Reid — and then head to bed for an early night. Saturday morning starts with yoga, meditation, and another group circle to center attention before the truffles get eaten. The effects of the psychedelic “trip” last from around 11 a.m. to 6 p.m., when members of the group return back to regular consciousness.

“In this time people are welcome to do what they feel like,” said Reid, “which might involve finding a quiet corner to sit, or meditating on their own. Or for some people it could be dancing around the garden.”

After dinner, everyone discusses their experience, which Reid says are often profound. “We describe the weekends as ‘conducive to mystical or spiritual experience,’ which does seem to be what people seem to take from it.” According to Reid, “the mystical experience” is well studied in psychotherapeutic literature, and has “these sixfold criteria: a sense of unity; a sense of sacredness; a sense of the uncovering of some kind of objective truth about reality; positivity and a sense of bliss; a sense of the transcendence of time and space; and finally, ineffability — the sense that people are unable to adequately describe these experiences in words.” It’s been said that tripping makes you feel one with the universe. “People are having experiences of this kind of nature at our weekends,” he told me.

Though the Psychedelic Society doesn’t frame these weekends as a medical treatment, it is this precise ability of psychedelics to provoke spiritual experiences which some psychiatrists suggest is crucial to their use in therapy. It’s jarring to realize, then, that getting approval to study them in a medical context (the recent ICL study was years in the making) requires navigating a lot of regulatory red tape. Psilocybin, LSD, and almost all major psychedelics are classified as Schedule I drugs, a status that defines them as of the most dangerous class, with a high potential for abuse and no accepted medical usage. (To put this in perspective, morphine, cocaine, methamphetamine, and fentanyl — the painkiller responsible for Prince’s overdose — are all Schedule II, while ketamine and anabolic steroids are Schedule III. Schedule V drugs represent the least potential for abuse.)

Though a Schedule I designation doesn’t exclude the possibility of research, it makes it very difficult. It’s hard to obtain funding from any major body, and the small number of studies that are funded must jump through lots of procedural hoops to comply with government regulation.

So how, exactly, did we end up in a situation where some of the most promising drugs for assisting psychotherapeutic treatment are also the most severely criminalized? Understanding this means looking back at the historical context of their discovery and subsequent journey from medical research drugs to countercultural catalyst.