Patterns of drug use and social attitudes to drug use have changed dramatically over time.
Britain initiated the Opium Wars (1839 and 1858) with China over the opium trade - not to stop the trade, but to ensure that British interests profited from it. The Chinese wanted to ban opium consumption and importation. The British demanded that the Chinese buy (and presumably consume) opium from the British East India Company.
The notion of making drug use illegal did not really emerge in western societies until the late nineteenth century. Before that, in Australia, Britain, Europe, and the United States, whether people used drugs was considered a personal decision - subject to social disapproval, but not illegal. Alcohol was of course the most widely used psychoactive substance.
Most of today's illegal drugs originally had medicinal uses. Opiates are very effective pain killers. Heroin, a very pure form of opiate, was developed - by the Bayer company - to treat wounded soldiers and send them back into battle as heroes (hence the name 'hero-in'). It was used medically in many countries for many years. Ecstasy (MDMA) was first synthesised in 1912, and later used in psychotherapy. Cocaine was advocated by Sigmund Freud as a cure for heroin addiction (and it was also once an ingredient in Coca Cola). Until the early twentieth century, cannabis could be bought over the counter and was used (often in tincture form) to treat a range of ailments.
Before the 1960s, when the notion of 'recreational' drug use became a cultural phenomenon, most instances of drug dependency resulted from medical uses of drugs like heroin and morphine.
The idea of prohibition
Internationally, the temperance movement, which had begun in the late eighteenth century, gained prominence in the late nineteenth century, advocating the legal prohibition of alcohol and other drugs. The temperance movement argued against drug and alcohol use on the grounds that it was morally irresponsible and caused violence, indolence, poverty and social decay.
Influenced by temperance activists, US President Theodore Roosevelt convened an international opium conference in Shanghai in 1909, which was followed by another conference in The Hague in 1911, which led to the International Opium Convention. This convention became the foundation for later international treaties and conventions on drug use.
The 1914 Harrison Narcotic Act banned the production and sale of opiates and cocaine in the United States, the first prohibitionist legislation (although in form it was a revenue act, requiring the registration of, and payment of special taxes by, producers, distributors and suppliers of opiates and cocaine). In practice, it led to the arrest of thousands of doctors, pharmacists and addicts. The prescription of heroin for medical purposes was not explicitly prohibited by the Harrison Act, but in 1919 the US Supreme Court ruled that the prescription of narcotics was a violation of the 'good faith practice of medicine', and therefore a criminal offence under the Act.
The temperance movement had its most well-known success in the United States when alcohol was legally prohibited in 1920 (under the Eighteenth Amendment to the Constitution, implemented by the federal Volstead Act and in many cases, state laws and local ordinances). The prohibition of alcohol was enforced enthusiastically - if unevenly - for many years, with special police squads used to crack down on both domestic distillers and alcohol smugglers. Organised crime gangs stepped in to produce and distribute alcohol, which continued to be very popular. Because it was easier to transport and to conceal, spirits took over from beer as the predominant form of alcohol. Alcohol consumption probably rose during the prohibition years. In 1933, the United States abandoned its alcohol prohibition experiment and the Volstead Act was repealed.
Cannabis was made illegal in a number of States in the 1920s, beginning with those States bordering Mexico or with large Mexican immigrant populations, and then spreading to others. Cannabis was prohibited federally in the United States by the 1938 Marijuana Tax Act (although it had already by then been banned in 26 States). Again, the Marijuana Tax Act was also strictly speaking a tax law, which imposed criminal penalties to punish use, possession, supply or cultivation.
Since the 1960s, the United States has waged a 'War on Drugs' both domestically and internationally. The Obama administration has abandoned the use of that language as counterproductive and has signalled a shift in resourcing towards treatment domestically. It remains to be seen whether there is a similar shift in its international policy. The United States has been the major funder and supporter of the International Narcotics Control Board, a UN body which monitors compliance with international drug treaties. There are several of these treaties - including the 1961 Single Convention on Narcotic Drugs - which require signatory states to pass laws to prohibit the use, possession, sale and production of drugs. Australia is a signatory to all the international conventions on psychoactive drugs.
At a state level, use or possession of cannabis is now legally available in 26 American states, in four states for any purpose (including recreational) and in the other states for medicinal purposes. There are a variety of different arrangements for the legal cultivation or sale of cannabis where there has been a law change.
These legal changes are largely the result of citizen-initiated referenda.
These developments have occurred over a relatively short period and it is likely that other states will also adopt less restrictive policies. It might be expected that growing public acceptance of these changes will impact on social attitudes to cannabis use in Australia as well as the United States, adding to pressure for change.
Ironically, as the historian Alfred McCoy has shown, while the United States has been the most vocal promoter of international drug prohibition, actions of the United States military have given the international drug trade its biggest boosts. First, in the Second World War, American military intelligence made arrangements with Sicilian mafia figures such as Lucky Luciano to support the Allied invasion of Italy. The arrangement allowed the mafia to gain control of - and expand - the international heroin trade, including into the United States. Later, in Vietnam, the CIA sought alliances with the hill tribes of the Golden Triangle against the communist Viet Minh. In exchange for their political support, the CIA provided substantial transport and other logistical support for the hill tribes to sell opium and heroin. And United States soldiers in Vietnam became the major customers for the heroin, in many cases taking their heroin dependence back home with them.
The Vietnam War contributed to the significant increase in drug consumption in Australia in the late 1960s, with American soldiers on 'rest and recreation' leave in Australia creating a market for heroin, marijuana and other illicit drugs, and providing a glamorous example for the locals.
In 1976, the Netherlands adopted a policy of selective enforcement of its cannabis laws. The prosecutors and police are instructed to not prosecute minor offenders, and to tolerate a retail supply of cannabis through cafes. The laws prohibiting the possession and use (and supply and cultivation) of cannabis are not actually repealed, but they are not enforced - selectively - by government policy.
Several European countries - notably Portugal - have since relaxed their laws (or law enforcement) about possession offences, sometimes just for cannabis. But other European countries continue with a predominantly prohibitionist legal system. Sweden claims to have achieved relatively low levels of drug use with a firm prohibitionist approach, which includes compulsory treatment of drug users, and considerable public resourcing of drug rehabilitation and education programs, after an earlier period of liberalisation.
The United Nations annual World Drug Report consistently estimates that about 245 million people (about 5% of the population aged 15-64) had used illicit substances at least once in the previous year. Cannabis remains the most commonly used illicit drug internationally, followed by amphetamine, opiates and cocaine. (World Drug Report 2015)
Harm reduction focuses on minimising the negative impacts associated with drug use, individually and socially. While not advocating drug use, supporters of harm reduction argue that we should accept that some drug use will occur, and focus on addressing the harms caused.
This alternative approach to prohibition gained support in the 1980s, especially in Europe and Australia, and found expression in a number of public health programs.
In response to the arrival of the HIV/AIDS pandemic in the mid-1980s, needle exchange programs were introduced in Australia and in several European countries with the aim of preventing infectious contact between intravenous drug users. Needle exchange programs remain criminalised in many American States.
Safe injecting rooms were introduced in Europe in the 1990s. In 1994 Switzerland began a program of heroin prescription to heroin dependent people who had consistently failed earlier attempts at rehabilitation. The thinking is that providing heroin to participants gives them a chance to achieve greater stability in their lives, not least because they do not have to devote substantial time and energy to obtaining and paying for heroin. Heroin prescription now operates in several European cities and Vancouver.