When a Plant Becomes a Drug: Prohibition, Moral Panic and Law

A legal category is not a botanical category

A botanist can describe a species, a chemist its compounds, and a physician its effects. Law does something different: it decides which parts of the plant, preparations, acts, and people are permitted, licensed, taxed, or punished. “Drug” is therefore not only a scientific description but also a legal and institutional label.

That matters because legal categories change over time. The same substance may be medicine in one regime, dangerous intoxicant in another, and tightly controlled medicine in a third. The category changes without changing the molecule; what changes is the regime around it.

Drug-control history is not a simple move from complete freedom to complete ban. States have used prescriptions, pharmacy records, import licences, taxes, sales restrictions, administrative offences, and criminal law. The word “prohibition” can therefore conceal very different mechanisms.

This article uses prohibition broadly for a regime that systematically pushes non-medical or unauthorized use outside the lawful sphere. For individual laws, however, we distinguish tax, registration, trade prohibition, possession prohibition, and criminal sanction.

The early twentieth century brought wider controls over opium, morphine, cocaine, patent medicines, and poisons. Part of this development responded to real problems of dependence, misleading remedies, and international trade; part reflected moral ideas about intoxication and the social groups associated with particular drugs.

Cannabis therefore entered an already structured legal field. By the time authorities treated it more harshly, administrative models, police institutions, and international forums already existed that could translate a substance into a category, permit, statistic, and offence.

Mexico prohibited the cultivation and trade of marijuana nationally in 1920, seventeen years before the U.S. Marihuana Tax Act. Historical research links this to domestic medical and legal discourses about madness, violence, degeneration, and “protection of the race,” not merely to pressure from the United States.

The case matters methodologically: if U.S. prohibition is explained simply as the export of one American industrial conspiracy, it cannot adequately explain why similar restrictive models developed elsewhere from their own political and health ideas.

The United States before 1937: state and local restrictions came first

Before the federal act, U.S. states and municipalities had already adopted restrictions. The National Academies summarize a mix of motives: anti-immigrant sentiment toward Mexicans, the broader temperance movement, social elitism, concern about youth, and fears linking intoxication with violence or madness.

It is therefore inaccurate to treat every early law as the direct product of one identical racist motive. Racialized arguments are documented, but their weight varies by place and time.

Spanish and Mexican-Spanish forms such as marihuana or mariguana predated the U.S. federal campaign of the 1930s. In the United States the term also became politically useful because it could distance the plant from pharmaceutical “cannabis” and associate it with Mexican foreignness.

The more precise claim is that U.S. media and institutions amplified the term within a particular political frame—not that one official invented it as a propaganda device.

Public rhetoric repeatedly associated cannabis, opium, and other drugs with ethnic minorities, immigrants, jazz culture, crime, and sexual danger. Such associations helped turn a question about substances into a question about “dangerous people.”

But three claims must be separated: racist rhetoric existed; it may have shaped policy adoption; and law may have been enforced unequally. All three matter historically, but they are not the same claim and each requires its own evidence.

In the 1930s many U.S. stories linked marijuana with insanity, murder, sexual disorder, and sudden loss of control. The Federal Bureau of Narcotics used and circulated such stories, although the sensationalist tradition did not originate in a single office.

When the anecdote becomes the representative image of an entire population, debate moves from measuring risk to confronting a symbolic threat. That is one of the central mechanisms of moral panic.

What does “moral panic” actually mean?

The term does not mean that no danger exists. In sociology it describes a process in which a practice or group becomes a symbol of wider moral breakdown, while media attention and political response can become disproportionate to the available evidence.

This article therefore does not use the phrase as an insult for every strict policy. We ask whether there are personified “folk devils,” repeated exaggeration, selective examples, and a rapid movement from fear to punitive control.

Harry J. Anslinger, the first commissioner of the Federal Bureau of Narcotics, became the central public face of the U.S. anti-marijuana campaign. He used dramatic case stories and embraced claims about violence, madness, and danger that are assessed far more critically today.

Recent historical work, however, argues that popular histories often inflate his role into that of a nearly solitary architect of the law. State pressure, medical beliefs, policing interests, and foreign prohibition precedents existed before federal action.

Newspapers in William Randolph Hearst’s empire published markedly sensationalistic marijuana stories. That is relevant evidence for media framing and for the construction of a public image of danger.

A much stronger claim is that Hearst coordinated prohibition in order to protect timber or paper interests from hemp. The historical evidentiary basis for that unified causal story is not comparable to the evidence for sensationalistic reporting.

A popular account claims that DuPont needed cannabis prohibition to protect new nylon from industrial hemp. A recent critical review of the 1937 law’s origins finds no documentary foundation for such a master plan and notes that the Marihuana Tax Act did not prohibit hemp fibre production.

Economic interests are a legitimate question in drug policy. But the fact that a law creates winners and losers does not itself prove that one industry secretly caused it.

1937: the Marihuana Tax Act used a tax mechanism

The 1937 U.S. Marihuana Tax Act was not written as a one-line ban on the plant. It created registration, taxes, order forms, and recordkeeping requirements for marijuana transfers, with severe consequences for activity outside the authorized system.

Despite its tax form, the practical legal effect was highly restrictive. It is a useful example of how a state can push conduct out of lawful space through administrative and fiscal machinery without relying on the simplest wording of “this is prohibited.”

During congressional hearings, William C. Woodward, speaking for the American Medical Association, opposed parts of the proposal and criticized reliance on anecdotes and the lack of adequate consultation with medical expertise. This primary record shows that “medicine” did not act as one unified pro-prohibition bloc.

The dispute also illustrates the difference between asking whether a substance has risks and asking whether a proposed law rests on sufficiently good evidence and an appropriate legal mechanism.

After 1937 the medical space for cannabis in the United States continued to shrink, and the plant was removed from the United States Pharmacopeia in 1942. Changing pharmacy, difficulty standardizing preparations, newer therapeutics, and anti-drug policy all formed part of that environment.

The history is therefore not a simple story of a “proven medicine” stolen entirely by politics. There were genuine problems of standardization and limited evidence, while legal control also reduced the plant’s medical normality.

During the Second World War the U.S. Department of Agriculture used Hemp for Victory to encourage hemp cultivation for rope, coarse cloth, and other military fibre needs. A government that had imposed strict marijuana tax controls only a few years earlier could treat the same plant as a strategic crop under a special regime.

This does not mean the law imposed no costs or obstacles on hemp. It does mean that the claim “the state prohibited cannabis in order to destroy fibre competition” fits the direct wartime record poorly.

After the war, policy shifted toward harsher penalties

U.S. policy in the 1950s tightened penalties through the Boggs Act of 1951 and the Narcotic Control Act of 1956, including mandatory minimum sentences for several drug offences. Public discourse increasingly connected drugs with youth, crime, heroin, and national security.

This was a different stage from 1937: the issue was no longer only a tax-administrative restriction on one plant but the expansion of a wider punitive apparatus over “narcotics” and other prohibited drugs.

The 1925 Geneva International Opium Convention brought cannabis into international control, particularly through rules governing international trade in Indian hemp, resin, and preparations. It was an important step, but it is inaccurate to describe it as the moment the world uniformly criminalized every domestic use of the plant.

The international system emerged in stages: trade and statistical control first, increasingly standardized national obligations later, and eventually a stronger norm of limiting use to medical and scientific purposes.

The 1961 Single Convention on Narcotic Drugs consolidated earlier treaties and placed cannabis and cannabis resin in Schedule I and also in the more restrictive Schedule IV framework then in force. It created broad obligations concerning cultivation, production, trade, and use.

Article 49 allowed only temporary transitional reservations for some traditional non-medical practices, while requiring non-medical cannabis use to be discontinued within twenty-five years at most. International law was therefore not simply recording national practice; it was reshaping local traditions toward a more uniform norm.

International control was not solely a policing project. Health experts, diplomats, and administrative institutions evaluated dependence, harm, and medical usefulness. But expert assessments were limited by the evidence and conceptual models available at the time and could later be revised.

This is the middle ground between two caricatures: cannabis was not controlled in the complete absence of health concern, but neither did health classifications arise in a vacuum free of political, cultural, and institutional values.

Colonial and geopolitical differences did not disappear inside one treaty

The international regime had to coordinate states and empires with very different traditions involving opium, coca, cannabis, and pharmaceutical markets. What one society treated as customary practice could appear elsewhere as a social danger or colonial administrative problem.

When those differences enter one treaty system, scientific language and diplomatic power operate together. The history of international drug control therefore cannot be read from pharmacology alone.

In the United States marijuana became increasingly visible among students, young white adults, and the counterculture. A substance previously framed as a problem of marginal or foreign groups now appeared inside more dominant social strata.

That changed the political problem. Debate was no longer only about the “dangerous other,” but about middle-class children, universities, protest movements, and a wider conflict over authority.

The U.S. Controlled Substances Act of 1970 created five schedules and placed marijuana in Schedule I from the outset. That category was legally associated with high abuse potential, no then-accepted medical use in the United States, and a lack of accepted safety for use under medical supervision.

The system matters because it made legal classification explicitly comparative: different substances received different levels of control. Yet the table remains an institutional judgment that the statute itself provides procedures to revisit.

1972: the Shafer Commission did not endorse the existing punitive model

The National Commission on Marihuana and Drug Abuse, created by Congress, published Marihuana: A Signal of Misunderstanding in 1972. It did not recommend a fully commercial legal market, but it concluded that criminal punishment of private possession and use was disproportionate and recommended a decriminalizing direction.

This is a key historical example of a gap between formal scheduling and the judgment of a commission specifically created to review the issue. Law and expert review can diverge without requiring one side to be treated as pure science and the other as pure propaganda.

The later U.S. “war on drugs” increased the policing, penal, and political weight of controlled substances. For cannabis it is especially important to the history of enforcement, large numbers of arrests, and unequal consequences—not as an explanation for every law created decades earlier.

Projecting later repressive outcomes backward into 1937 as a pre-planned final objective confuses the consequences of long institutional development with evidence of original intent.

A law with multiple origins can still be enforced discriminatorily. Modern reviews of U.S. cannabis policy emphasize racial inequality in criminalization and in research consequences, and the fact that prohibition has burdened communities differently.

That must be kept distinct from the claim that every individual legislative provision was enacted exclusively because of racism. Equality of origin and equality of effect are different research questions.

Real risks do not determine criminal policy by themselves

Cannabis can acutely impair cognition and motor performance, and some users develop cannabis use disorder; driving, age, frequency, and high-THC products also matter. Public-health concerns should not be erased from history simply because earlier campaigns exaggerated them.

But health risk alone does not decide whether the better response is criminal prosecution, a licensed market, medical control, age restriction, taxation, or another policy. That second step is normative and institutional.

If legal categories were a simple reflection of pharmacological harm, all psychoactive substances would fall into a stable order under one shared metric. In practice alcohol, tobacco, opioids, stimulants, and cannabis have different historical institutions, cultural legitimacy, and legal regimes.

The comparison does not prove any substance “safe.” It shows that legal status reflects multiple criteria and path dependence, not laboratory risk alone.

Every regulatory regime redistributes costs and benefits. Pharmacists, farmers, police, prisons, fibre industries, traders, and later legal cannabis firms can all have interests. That is a normal subject of political economy.

The methodological error begins when the existence of an interest is treated as proof of hidden causation without an archival bridge connecting the two. This article therefore includes economic motives but rejects the rule “who benefited must have caused the law.”

Categories can be revised without control disappearing

After formal review in 2018–2019, WHO recommended changes to the international scheduling of cannabis. In December 2020 the UN Commission on Narcotic Drugs removed cannabis and cannabis resin from Schedule IV of the Single Convention while retaining them in Schedule I and therefore under strict international control.

This was not legalization. It is, however, important evidence that institutional judgments about the balance of harm and medical value can change with new evidence without the control system itself disappearing.

For any large causal story, use four questions. Is there a primary source explicitly linking the motive to the law? Was the motive present before the decision? Does it explain more than competing accounts? And can the story explain evidence that cuts against it?

This test weakens both old propaganda about “murderous marijuana” and modern internet stories in which one newspaper owner, one chemical company, or one official supposedly explains almost a century of global drug policy.

Cannabis did not become a legal “drug” in a single day. Local restrictions, health classifications, trade controls, and moral narratives emerged in different jurisdictions; tax, criminal, and international systems then tied these fragments into a more durable institution.

This article therefore ends with a double conclusion. Prohibition is not a neutral automatic translation of science into law, but neither is it one hidden conspiracy. It is a historically assembled system in which real risks, prejudice, media, expertise, government, and interests can combine into a legal category that then begins producing consequences of its own.