Mary Ann Sieghart: Restore sanity in the debate on drugs

America declared war on drugs 40 years ago. You'd think that by now, it might have won. Instead, any US teenager can buy cannabis, at higher strength and at a lower price. Meanwhile, severed heads are rolled across floors in Mexican discos and innocent people are scared to leave their homes in cities such as Ciudad Juarez, where the war on drugs has taken its highest toll.

Joseph McNamara is the retired police chief of San Jose. Writing in the San Francisco Chronicle, he says:"Like an increasing number of law enforcers, I have learned that most bad things about marijuana, especially the violence made inevitable by an obscenely profitable black market, are caused by the prohibition, not by the plant."

McNamara has been fronting a TV campaign for Proposition 19. When Californians go to the polls tomorrow in the US mid-term elections, they will also vote on this proposition, allowing cannabis to be legalised, regulated and taxed in the state. The "yes" campaign has been boosted by a $1 million donation from the billionaire financier George Soros, and its supporters are energised. Thousands descended on Washington at the weekend to take part in the comedian Jon Stewart's Rally to Restore Sanity.

Sanity is exactly what is needed in America's approach to drugs. As Abraham Lincoln said in 1840, "A prohibition law strikes a blow at the very principles upon which our government was founded." The principles of liberty and the pursuit of happiness are certainly infringed by laws that punish adults for lighting up in the privacy of their own home. But, principles aside, it's not as if prohibition has even worked.

The International Centre for Science in Drug Policy has recently published two devastating research papers. In one, it found an extremely strong link between anti-drug law enforcement policies and rises in drug-related crime, murder and gun violence. You can see the evidence in Mexico: since President Calderon launched his "war on drugs" against the cartels in 2006, some 28,000 people have been killed. The other study shows that the surge in US anti-drug funding between 1990 and 2007 has utterly failed in its purpose. In that time, the strength of cannabis has increased – there has been a 145 per cent rise in its active ingredient, THC. And its price, after inflation, has fallen by 58 per cent. Meanwhile, 80-90 per cent of Americans in their last year of high school say it is "very easy" or "fairly easy" to obtain.

Quite apart from the violence, look at the harm prohibition does. Every year, some 750,000 Americans are arrested for possession of small quantities of cannabis. That is a waste of time and money for the police and the criminal justice system. Meanwhile, black and Hispanic citizens are more likely to be arrested for possession of marijuana, even though white people are more likely to smoke it. So prohibition does nothing for race relations.

A study by the libertarian Cato Institute has calculated that legalising cannabis would save $8.7bn in the costs of policing and criminal justice and raise another $8.7bn in tax revenue. In California alone, where marijuana is the state's biggest cash crop, legalisation would save about $1.4bn and raise another $1.4bn. In a state with a $19bn budget deficit, that's a tidy sum.

The advantage of legalising and regulating, rather than simply decriminalising, is that the production and sale of cannabis is taken out of the hands of organised crime and given to legal producers and suppliers. Given that Mexican drug cartels earn 60 per cent of their revenue from cannabis, this could have a dramatic effect.

But it also means that quality and strength can be regulated. Many users don't want to fry their brains with skunk; they would prefer a milder high from cannabis with a lower THC content. When sold on the street wrapped in clingfilm, its strength is much harder to judge than when it's legally produced and sold in a reputable shop. Outlets could also insist on proof of age – Proposition 19 would make cannabis legal only for those over 21.

But what about the dangers of cannabis? Well, first, it's not clear that legalisation would increase consumption. Countries with lax drug regimes don't have more drug-taking than strict ones. Portugal decriminalised cannabis in 2001 and, after a small increase in the first two years, adolescent use of cannabis has been in decline ever since. The Netherlands, with its permissive approach, has a lower rate of consumption than Britain. Even if Proposition 19 did encourage more Californians to smoke weed, that would probably be at the expense of drinking alcohol. It's no surprise, then, that the California Beer and Beverage Distributors Association is one of the biggest backers of the "no" campaign.

Would a slight shift from alcohol to cannabis be such a bad thing? Alcohol is implicated in far more crime and anti-social behaviour than cannabis. It leads to far more disease and injury. It is far more addictive. Yes, skunk has been known to lead to psychotic episodes in young people already predisposed to schizophrenia; but there is also such a thing as alcohol-induced psychosis. Neither drug is harmless, but scientists rank cannabis below both alcohol and tobacco in the damage it causes. And under Proposition 19, driving under the influence would remain illegal and employers could still prohibit employees from working while stoned.

So what are the chances of it passing? Recent polls show the two sides are neck-and-neck. But what's interesting is that 90 per cent of Californians under 30 who are likely to vote are aware of the Proposition. Many Democrats believe that these young people, who may have been motivated to turn out by the prospect of legalising pot, will vote for Democrat candidates at the same time.

Not that this is an entirely partisan issue any more. Surprising numbers of Republicans are supporting legalisation, either on libertarian grounds or because of the money it could raise and save. Even Glenn Beck, the Tea Party-supporting shock jock, came out in favour earlier this year. And Sarah Palin questioned whether police should be wasting their time on it. Gary Johnson, the Republican former governor of New Mexico and a possible presidential candidate in 2012, has said, "Proposition 19 has the opportunity to be the domino that could bring about rational drug policy nationwide."

If anything, it is easier for a Republican to say this sort of thing. In public, at least, Democrat politicians are still wary of associating themselves with legalisation. In private, though, many Democrat strategists will be watching the vote carefully. In the 2008 presidential election, there was a big increase in turnout among young people, and they backed Barack Obama over John McCain by a factor of two to one. If Proposition 19 helps to energise the youth vote this year, expect many more states to have cannabis legalisation on the ballot in 2012. In that case, President Obama may well owe his re-election to the legacy of Cheech and Chong.

m.sieghart@independent.co.uk

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