In June 1971, US President Richard Nixon declared a "war on drugs". Drugs won.
The policy of deploying the full might of the state against the production, supply and consumption of illegal drugs has not worked. Pretty much anyone in the developed world who wants to take illicit substances can buy them. Those purchases fund a multibillion dollar global industry that has enriched mighty criminal cartels, for whom law enforcement agencies are mostly just a nuisance, rarely a threat. Meanwhile, the terrible harm that drug dependency does to individuals and societies has not been reduced. Demand and supply flourish.
"It is time to admit the obvious," writes Fernando Henrique Cardoso, former president of Brazil, in the Observer today. "The 'war on drugs' has failed."
Earlier this year, Mr Cardoso co-chaired the Latin American Commission on Drugs and Democracy with former presidents of Colombia and Mexico. They endorsed a collective shift in policy from repression of drug use to harm reduction. Last month, Argentina's supreme court declared the prosecution of individuals for the possession of small amounts of drugs to be unconstitutional. Colombia's constitutional court came to a similar conclusion in 1994.
The trend towards decriminalisation in Latin America is born of desperation. The continent is the world's largest exporter of cocaine and marijuana. Its economies and criminal justice systems have been corrupted by the trade; in some areas the power of the drug gangs rivals that of the state. Something had to change.
Something must change also in the countries that buy Latin America's biggest export. In Britain, more than half a million people aged 16-24 took cocaine last year, according to Home Office statistics. More than a third of all Britons aged 16-59 have taken drugs at some point in their lives; one in 10 in the last year.
Not all of those people are a menace to society. Most of them are not even a menace to themselves. Most who take drugs in their youth stop later on. A generation that has grown up with normalised recreational drug use now occupies the commanding heights of business, media and politics. They might not take drugs themselves, but they are not morally outraged by them.
That is a significant cultural change. The political fixation on drugs prohibition really took hold in the west in the 1960s as much from moral panic about a subversive counterculture as from analysis of the harm caused by particular drugs.
Since then, the law has tried to maintain a distinction between reputable and disreputable substances that neither users nor medical research recognise. Scientific attempts to classify drugs in terms of the harm they do – to the body and society – routinely place tobacco and alcohol ahead of cannabis and ecstasy. The point is not that the wrong drugs are banned, but that the law is nonsense to anyone with real knowledge of the substances involved.
One point of general agreement is that heroin is the big problem. It is highly addictive and those who are dependent – up to 300,000 in Britain – tend to commit a lot of crime to fund their habit. But then it is hard to tell how much of the problem is contained by prohibition and how much caused by it.
Leaving gangsters in charge of supply ensures that addicts get a more toxic product and get ever more ensnared in criminality.
Those arguments do not prove that the solution lies in legalisation, or even just decriminalisation. But as Mr Cardoso argues: "Continuing the drugs war with more of the same is ludicrous."
The entire framework of the debate must change. In Britain, we operate with laws that start from the premise that drug use is inherently morally wrong, and then seek ways to stop it. Instead we must start by evaluating the harm that drug use does, and then look for the best ways to alleviate it; and we must have the courage to follow that logic wherever it leads.
