Johann Hari: The one reason I will miss Milton Friedman

Over 40 years, he made the smartest case for the full legalisation of drugs that we have seen

Even in death, the Right misses the point. Milton Friedman - the Messiah of Monetarism, saviour of small-state conservatism - is about to be buried, but his mourners have conspicuously failed to laud his one great argument.

In the past week, his conservative obituarists have concentrated on the slew of issues he got wrong, lathering praise on his claims that a limp, slashed-back state delivers greater social mobility and a broader middle class than a mixed social democratic economy. Just compare Sweden and Texas to test that one. Yet, on one issue, Friedman applied the forensic brilliance of his brain to a deserving purpose: over 40 years, he offered the most devastating slap-downs of the "war on drugs" ever to be written.

He was a child when alcohol was criminalised in America. The Prohibitionist crusade to banish the "demon rum" and dry out the United States lasted until he was in his twenties. The lessons lasted his lifetime. He saw that even when you use force to prevent people from using a popular intoxicant, you don't actually reduce its use very much. "I wasn't very old, and was not much of a drinker, but there was no difficulty in finding speakeasies," he explained.

But while prohibition didn't succeed in the fantasies of its fans that it would "end alcoholism", it did succeed in one respect. It handed a massive industry to armed criminal gangs, who succeeded in ramping up the murder rate up by 78 per cent and making a mockery of the rule of law. "We had this spectacle of Al Capone, of the hijackings, of the gang wars..." Friedman wrote. "Prohibition is an attempted cure that makes matters worse - for both the addict and the rest of us."

Friedman saw - way ahead of almost any other commentator - how prohibiting cannabis, cocaine and heroin would spawn a thousand Capones. He warned: "Al Capone epitomises our earlier attempt at prohibition; the Crips and Bloods epitomise this one." The Chicago gangster famously gunned down six of his alcohol-hawking competitors on St Valentine's Day in 1929. But in the age of drug prohibition, there are equivalent dealer shoot-outs every minute of the day in South Central Los Angeles - and in Hackney, Bogota and Kabul. Late in his life, Friedman calculated that 10,000 people died this way every year in the US alone, equivalent to more than three September 11ths. Most were bystanders caught in the cross-fire.

And by globalising this puritanical war on drugs, the US government has globalised this gangsterism. Friedman warned that the war on drugs has "condemned hundreds, perhaps thousands, of Colombians to violent death". I have just returned from Mexico, which is rapidly Colombianising, with areas controlled by drug mafias who bribe or out-gun the police force and terrorise the local population. The same thing is happening on a huge scale in Afghanistan. "By what right do we destroy other people's countries this way?" Friedman demanded.

But armed gangsters are not the only species of crime generated by prohibition. Friedman proved that criminalising drugs causes an explosion in muggings and burglary, making us all victims of this war at some time in our lives. How? A kilo of heroin passes through six different dealers in the supply chain before it reaches the veins of a Londoner. Each link in the chain demands a fat fee for risking jail. This means heroin costs 3,000 percent more than it would in a legal, risk-free market - so a heroin addict must steal 3,000 per cent more to buy it; 3,000 per cent more grannies mugged, 3,000 per cent more homes burgled.

That's why so many police officers are now coming out in favour of unpicking hard-line prohibition and prescribing heroin, with Howard Roberts, the deputy chief constable of Nottinghamshire, joining the queue yesterday. They know from the experience in Switzerland - an ultra-conservative country that now nonetheless prescribes heroin - that it a silver bullet (or syringe?), bringing crime rates crashing down.

This does not mean Friedman was in favour of drugs. Friedman thought (rightly) that heavy drug use - whether it was alcoholism, cannabis addiction or junkiedom - was a human disaster. He once told Bill Bennett, Bush Snr's drugs tsar: "You are not mistaken in believing that drugs are a scourge that is devastating our society. Your mistake is failing to recognise that the very measures you favour are a major source of the evils you deplore."

He proved, for example, that prohibition changes the way people use drugs, making many people use stronger, more dangerous variants than they would in a legal market. During alcohol prohibition, moonshine eclipsed beer; during drug prohibition, crack is eclipsing cocaine. He called his rule explaining this curious historical fact "the Iron Law of Prohibition": the harder the police crack down on a substance, the more concentrated the substance will become.

Why? If you run a bootleg bar in prohibition-era Chicago and you are going to make a gallon of alcoholic drink, you could make a gallon of beer, which one person can drink and constitutes one sale - or you can make a gallon of poteen, which is so strong it takes 30 people to drink it and constitutes thirty sales. Prohibition encourages you produce and provide the stronger, more harmful drink. If you are a drug dealer in Hackney, you can use the kilo of cocaine you own to sell to casual coke users who will snort it and come back a month later - or you can microwave it into crack, which is far more addictive, and you will have your customer coming back for more in a few hours. Prohibition encourages you to produce and provide the more harmful drug.

For Friedman, the solution was stark: take drugs back from criminals and hand them to doctors, pharmacists, and off-licenses. Legalise. Chronic drug use will be a problem whatever we do, but adding a vast layer of criminality, making the drugs more toxic and squandering £20bn on enforcing prohibition that could be better spent on prescription, prevention and rehab, has failed, utterly. "Drugs are a tragedy for addicts," he said. "But criminalising their use converts that tragedy into a disaster for society, for users and non-users alike."

Today, an end to drug prohibition seems like a distant fantasy. But in 1924, even as vociferous a wet as Clarence Darrow was in despair, writing that it would require "a political revolution" to legalise alcohol in the US. Within a decade, it was done. We are approaching a tipping-point in the drugs debate. As we wait, I can still hear Milton Friedman in one of his last interviews, demanding: "In the meantime, should we allow the killing to go on in the ghettos? 10,000 additional murders a year? In the meantime, should we continue to destroy Colombia and Afghanistan?"

j.hari@independent.co.uk