Natalie Ginsberg, policy director of Multidisciplinary Association for Psychedelic Studies (Maps), who helped write the California's bill, said it was part of an "exciting" trend of US states learning from and building on each other's work.
Some of the earliest states to legalise cannabis offered no way to clear convictions, allowing white entrepreneurs with spotless records to dominate the "green gold rush" at the expense of their disproportionately black predecessors who had been arrested in previous years.
Alongside drugs, Wiener's bill would decriminalise various methods of checking safety and purity to reduce overdoses, and set up a commission to explore legalising psychedelics for medical and spiritual purposes.
Indigenous Americans have used mescaline and psilocybin mushrooms, supposedly called "flesh of the gods" by the Aztecs, for millennia. The bill specifically excludes peyote, a psychoactive cactus which is federally permitted as a sacrament but highly endangered.
More recently, California's thriving drug culture has made it a locus of both above-board and illicit research and treatment. Ginsberg said that many therapists who used MDMA in the 70s believed so strongly in their work that they "went underground" when it was banned. Decriminalising could make the practice safer, although that is not the bill's goal.
Iryna Aronov, a Mountain View therapist who helps people make sense of traumatic drug experiences, said criminal sanctions make it easier for users to have bad trips, imagining police officers everywhere. She said that the stigma also leads some therapists to dismiss positive use as "just getting high", shaming patients and blocking their healing.
However, Dr Paul Abramson, a federally licensed ketamine therapist and director of My Doctor Medical Group in San Francisco, said the bill would make no immediate difference to most clinicians' actual practice, since it will not change medical regulations.
He said the inclusion of ketamine was "highly problematic" because, unlike "classical psychedelics", it is very addictive. Although he believes in general decriminalisation as a way of reducing harm, he urged caution for patients attempting DIY psychedelic therapy.
"These are real medications, and like all medications they have side effects," he said, noting that psychedelics can exacerbate manic and psychotic episodes.
