In the past few years, several studies about the positive mental health effects of “magic mushrooms” have prompted Oregon, Colorado and several U.S. cities to decriminalize psilocybin, the drug certain fungi produce naturally. California, which passed a bill legalizing the mushrooms and several other natural psychedelics in September, will not be joining them. On October 6, Governor Gavin Newsom vetoed the bill that would have legalized the use of several hallucinogens in the state.

The vetoed bill would have allowed those over 21 to possess psilocybin and dimethyltryptamine (DMT) mescaline (excluding peyote). Senate Bill 58, sponsored by Senator Scott Wiener (D-San Francisco), would have legalized the personal possession, cultivation, and use of DMT, along with psilocybin and psilocin, which are the primary ingredients in magic mushrooms. It capped the permissible amount of the “magic mushroom” drug components at one gram and DMT at four grams.

Although he vetoed the bill, Newsom did not completely shut the door on future decriminalization legalization. Rather, in a statement he issued, he called for additional work to “set up regulated treatment guidelines—replete with dosing information, therapeutic guidelines, rules to prevent exploitation during guided treatments, and medical clearance of no underlying psychoses.” He said he could not sign a bill to “decriminalize possession prior to these guidelines going into place.”

Newsom also said that while he favors “new opportunities to address mental health through psychedelic medicines like those addressed in the bill,” regulations are needed before the substances can be legalized.

Weiner’s bill, which would have decriminalized the listed drugs as of January 1, 2025, also ordered California’s Health and Human Services Agency to create a “working group” to study all the newly legal substances and recommend measures that would regulate their therapeutic use.

Psilocybin, which a person’s intestines will convert into psilocin, has also shown positive effects in treating headaches, anxiety, anorexia, obsessive-compulsive disorder, and various forms of substance abuse.

The therapeutic use of psilocybin and other psychedelics has been documented in many recent studies. In January 2023, the Los Angeles Times reported that MAPS Public Benefit Corporation, a private California biopharmaceutical company, “announced positive results from a study of MDMA (commonly known as ecstasy or Molly) for the treatment of post-traumatic stress disorder (PTSD). MAPS CEO Amy Emerson told Forbes that MDMA therapy is “a potentially new breakthrough therapy to treat individuals with PTSD—a patient population that is often left to suffer for years.” MAPS is expected to submit its new drug application to the Food and Drug Administration in the third quarter of 2023.

In addition, the peer-reviewed journal JAMA Psychiatry (formerly the Archives of General Psychiatry) reported that “psilocybin-assisted psychotherapy was an “effective and quick-acting treatment for a group of 24 participants with major depressive disorder.”

Perhaps the most hopeful and disappointed proponents of legalization are veterans. Jesse Gould, the veteran founder of the “Heroic Hearts Project” told Forbes, “Every day that criminal penalties prevent veterans from accessing psychedelic plant medicines is a day their lives are at risk. Psychedelics helped heal the unseen scars from my service in the War on Terror after traditional medicine failed me for years…Removing criminal penalties for the use of these substances will help that work, not hurt it.”

In agreement with those sentiments, Senator Wiener said of the veto, “The veto is not the end of our fight,” and pledged to reintroduce legislation for next year that would focus on the therapeutic use of the psychedelics, as Newsom requested.

“This is a setback for the huge number of Californians — including combat veterans and first responders — who are safely using and benefiting from these non-addictive substances and who will now continue to be classified as criminals under California law,” Wiener said. “Today’s veto is a huge missed opportunity for California to follow the science and lead.”

Paul Stamets, a mycologist or expert in fungi, agrees. He told CNN, “Let’s be adults about this. These are no longer ‘shrooms.’ These are no longer party drugs for young people. Psilocybin mushrooms are non-addictive, life-changing substances.”

Not everyone supports decriminalization. Opponents, many of which are law enforcement groups and some members of the medical field, opposed the bill. One of them, Jennifer Mitchell, a neurology professor at the UC San Francisco School of Medicine, agreed with Newsom’s veto and told the Los Angeles Times that decriminalizing personal use before developing an infrastructure that would ensure safety and education could lead healthcare professionals to see “more adolescent use than we already do because it will give (them) a green light.”