The Origins of Cannabis Prohibition

A plant with a paper trail longer than its prohibition

Somewhere around 2700 BCE, Chinese pharmacopoeias were already cataloguing Cannabis sativa as a medicinal plant. Let that sit for a moment. The prohibition era we're living through , or, depending on where you are, living past , spans roughly a hundred years. The documented relationship between humans and this plant stretches back nearly five thousand. That asymmetry matters when you're trying to understand how we got here.

I've spent a fair amount of time lately digging through the legislative history of cannabis, partly because the science of cannabinoids makes a lot more sense once you understand why so much of it stalled for so long. If you want to understand what tetrahydrocannabinol actually is and how it behaves in the body, you'll eventually bump into the question of why it took until 1964 for Raphael Mechoulam and Yechiel Gaoni to isolate and describe it properly. The answer has almost nothing to do with scientific difficulty and almost everything to do with political classification.

Before prohibition: a long history of use

Cannabis has appeared in the historical records of ancient India, Egypt, Greece and Persia in contexts ranging from ritual to rope-making. In India, the preparation known as bhang , dried leaves and flowers ground into a paste or drink; has been documented in texts associated with Ayurvedic tradition for millennia. Arab physicians wrote about it in the medieval period. European physicians encountered it through colonial contact and trade routes.

By the 19th century, tinctures made from cannabis extract were listed in the British Pharmacopoeia and widely stocked in Western dispensaries. The Irish physician William Brooke O'Shaughnessy deserves a mention here: after documenting cannabis preparations he observed during his time in India in the 1830s, he brought extracts back to Britain and published clinical observations that sparked genuine scientific interest. This wasn't fringe herbalism. It was mainstream medicine.

What the 19th century pharmacist was working with, of course, was largely undefined. Nobody yet understood the endocannabinoid system, that wouldn't be mapped until the late 1980s and 1990s, or the specific compounds involved. The pharmacological picture was incomplete. But the point is that cannabis entered Western medicine through legitimate channels and sat there, relatively undisturbed, for decades.

The early 20th century shift: race, politics, and the Marihuana Tax Act

The story of how cannabis became a prohibited substance in the United States is, honestly, not a flattering one. It is tangled up with anti-Mexican immigration sentiment in the American Southwest, with the career ambitions of Harry J. Anslinger; the first commissioner of the Federal Bureau of Narcotics, and with a press environment that was happy to print sensational stories linking cannabis use to violence and racial mixing.

The word "marihuana" itself was a deliberate choice. Cannabis was already a known word, associated in the public mind with medicine and with the extract on pharmacy shelves. "Marihuana" carried a foreign connotation, associating the plant with Mexican immigrants in states like California, Texas and Colorado. Whether this was calculated or simply reflected ambient prejudice is debated by historians, but the effect was the same: the rebranding helped sever the public's mental connection between the familiar pharmacy product and the new moral panic.

Anslinger's 1937 campaign for the Marihuana Tax Act drew heavily on anecdote and inflammatory rhetoric. Academic and medical voices pushed back at the time, the American Medical Association sent a representative to congressional hearings who objected to the framing; but the Act passed anyway. It imposed a prohibitive transfer tax on cannabis that effectively ended commercial distribution.

I'll admit this part of the history genuinely surprised me when I first went looking at primary sources rather than summaries. The scientific opposition was more present and more articulate than the conventional narrative suggests. It was overridden, not absent.

The international architecture: the 1961 Single Convention

The United States was not alone for long. The 1961 UN Single Convention on Narcotic Drugs created an international scheduling framework that placed cannabis in Schedule IV, the most restrictive category, alongside substances considered to have "particularly dangerous properties." This classification placed cannabis alongside substances that the convention described as having limited or no medical value and significant abuse potential.

Australia adopted this international framework through its own domestic legislation. The various state and territory Poisons Acts, later harmonised through the Poisons Standard (formally the Standard for the Uniform Scheduling of Medicines and Poisons, administered by the TGA), progressively restricted cannabis across Australian jurisdictions through the 1960s and 1970s. By 1987, the Poisons Standard had placed cannabis and its primary psychoactive constituent into what would become Schedule 9 (Prohibited Substance), with narrow exceptions for research.

Schedule 8 (Controlled Drug) and Schedule 4 (Prescription Only) pathways for cannabis-derived medicines only began to re-emerge in Australian law much later, culminating in the TGA's 2016 amendments that created a regulated access pathway for medicinal cannabis products and, subsequently, the Special Access Scheme and Authorised Prescriber frameworks that allow clinicians to legally prescribe approved products today.

What prohibition cost the science

This is where the history intersects directly with research literacy, which is my particular obsession. Schedule I classification in the United States (the equivalent of Australia's Schedule 9) did not make cannabis research impossible, but it made it extraordinarily slow and expensive. For decades, researchers who wanted to study cannabis had access only to a single government-approved source; the University of Mississippi, and the material supplied was frequently low in THC and not representative of what was actually being consumed in the community.

This matters when you're reading the literature. Studies conducted prior to roughly 2010 often used material that was chemically quite different from contemporary cultivars. Comparisons across eras are difficult. Effect sizes from older studies should be read carefully against their methods sections, not just their abstracts. It's a problem the field is still partly working through.

The isolation of the endocannabinoid system, the discovery of CB1 receptors in 1988 by Allyn Howlett and William Devane, and anandamide in 1992 by Mechoulam's group; happened despite the scheduling environment, not because of any change in it. The science moved; the regulation didn't, at least not quickly.

And in my view, the scheduling of cannabidiol alongside THC for most of this period represents one of the more counterproductive regulatory decisions of the 20th century. CBD does not produce the psychoactive effects associated with THC; the 1961 convention's framing treated the whole plant as uniformly hazardous, which subsequent chemistry has not borne out. The TGA didn't reschedule low-dose CBD to Schedule 3 (pharmacist-only, over-the-counter) until 2021, and only under tightly defined conditions.

The uneven unwinding

The past decade has seen significant regulatory movement globally, but it has been patchwork. Uruguay became the first country to fully legalise recreational cannabis nationally in 2013. Canada followed in 2018. In the United States, legalisation has proceeded state by state, producing a confusing patchwork of state law sitting against a federal Schedule I classification that has not formally changed.

Australia's path has been different again. The 2016 regulatory amendments focused on medicinal access, not broader legalisation. The ACT introduced personal-use decriminalisation in 2020, but that applies only within that territory and does not change the Commonwealth scheduling position. The picture is genuinely complicated, and anyone telling you it's simple is probably selling something.

What the history makes clear is that the current regulatory architecture was not designed around pharmacology. It was designed around a particular set of political and social forces that were active in the 1930s and institutionalised in 1961. The science of the plant, its constituent cannabinoids, its interaction with the body's own endocannabinoid receptors, was largely unknown at the time those frameworks were built. We are now doing the work of filling in a picture that prohibition delayed by half a century or more.

I went for a swim at Bellerive Beach this morning in water cold enough to make my cattle dog give me a look of genuine concern. Came back and kept reading. The history of cannabis prohibition is, in the end, a good reminder that classification systems are human artefacts, made under specific pressures, and subject to revision when the evidence base changes. That's not an argument for any particular policy position. It's just how science and law actually work.

Sources

• Scheduling Policy Framework for Medicines and Chemicals; TGA, Australian Government
• Cannabis and the Endocannabinoid System, National Library of Medicine, NCBI
• The International Drug Control Conventions, United Nations Office on Drugs and Crime
• Cannabis Drug Facts; Alcohol and Drug Foundation, Australia

, Hannah Bui, Evidence & research-literacy writer