Picture this: beside the electric toothbrushes at your local chemist, you can pick up complete kits of syringes, needles, cotton balls, lighters, rubber tying-off cords and cute stainless-steel spoons - all vacuum-sealed in plastic. Just as you can request some high-strength cortisone cream to treat that pesky eczema on your shin, you can ask your GP for heroin. Thus you can hand the pharmacist an NHS prescription for a two-week supply of commercial opiates (let's say Merck's version is called Scagodrine), inviting nary a raised eyebrow. As with all NHS prescriptions, your co-payment will only amount to about £6.50. You can walk out of the chemist with your Boots Home Works Kit and Scagodrine (bagged into single dosages whose potency is printed on the box), and wave to the bobby on the corner. He'll wave back.

Are you, in your mind's eye, scampering down to your nearest surgery for that prescription, and racing off to Boots? Perhaps you're thinking, "Blimey, all this time I haven't been an intravenous drug addict because heroin is against the law! If I wouldn't get arrested, I'd spend every day in an apathetic swoon, alienate my friends and lose my job!"

Most of us aren't heroin addicts because we don't want to be heroin addicts. Or coke heads or meth freaks. The people who do want to be junkies are junkies. Were hard drugs decriminalised, it's dubious that consumption would appreciably rise.

Which is why Lib Dem MEP Chris Davies's calling for the legalisation and regulation of hard drugs last week really shouldn't qualify as "brave". Nor should Lord Birt's now partially leaked 2003 report on UK drug policy qualify as "controversial". The report's assertions make common sense: for drug cartels, government seizures are merely a modest line-item in their budgets; the "maximum" - meaning, farcically optimistic - estimate of drug seizures runs to 25% of total supply. Confiscation only serves to drive up the street price of hard drugs and so benefits their purveyors. Therefore, even more effective narcotics enforcement would simply push users into stealing yet more DVD players to fund costlier habits.

Alas, common sense is in short supply on this matter. The west's prohibition approach to drugs is as entrenched as it is idiotic. Davies and Birt are pissing in the wind. So, by the way, am I. But I've nothing else to do this afternoon, so let's fritter away my time.

It would be nice if everyone were happy and good. If everyone were a productive member of society, reliably rising to greet the morning, bursting into song and eager for the day ahead. If we all took such joy in the miracle of sheer being that it would never enter our heads to try to fuzzy up a single blade of grass.

But government can't manifest this healthy look-life-square-in-the-eye by fiat. Frankly, most of us need to take the edge off once in a while - or put it on. Get a buzz from a cup of coffee or a few drags of a fag. Put our feet up with a glass of cabernet or sink into the sofa with a cognac before bed. Plenty of folks in my boomer generation still suck on the odd spliff in the privacy of their living rooms, and the sky doesn't fall when they do.

If most of us tinker with our consciousness on occasion, a subsection of our fellows finds raw reality not just hard to take, but unbearable. Whether to induce exhilaration or oblivion, the compounds are out there to do the job, and these people, by hook or by crook, are going to get their mitts on those drugs.

There may be a set percentage of the population determined to throw their lives away. Calling drug abuse a "victimless crime" may be a misnomer, for you can victimise yourself. Be that as it may, we've plenty of evidence by now that it costs a society far more to try to stop people from "self-medicating" than to let them. It's hard enough to protect people from each other; it's impossible to protect people from themselves.

Davies was dead sound in calling for an end to drug prohibition in the name of mere "harm reduction". There's no good answer here. But the costs of this puritanical thou-shalt-not are gobsmacking. We've delivered whole countries such as Afghanistan largely into the hands of crooks. Internationally, we've created a massive shadow economy out of the reach of the law. On the US-Mexico border, murderous battles between rival drug gangs are getting so out of hand that this month Arizona and New Mexico declared states of emergencies. In the UK alone, crimes committed by heroin and cocaine addicts to feed their habits come to £16bn a year.

We can take Vioxx off the market, but the appetite for pain relievers of the dodgy variety is not going to go away, no matter how many scary adverts run on television. So deal with it. Regulate drugs, tax them, monitor them, just like alcohol. You'd take preying on that appetite away from elements that have grown so powerful that they constitute rival governments. You'd have far few drug-related deaths, because the product would be pure, its potency established. You'd clear prisons of people guilty of nothing more than wanting to feel different, and you'd free up the police force to go after people who actually want to hurt somebody else. You'd take the cultural shine off drugs altogether, depriving them of their furtive cachet.

Isolated European experiments with more liberal drug policies have poorly tested the premise that prescription beats proscription. When a single country such as the Netherlands loosens its narcotics laws while its neighbours continue to pursue punitive ones, naturally the country becomes a magnet for wasters, and there goes the neighbourhood. A Europe-wide rethink would spread the wasters around.

Yet as for working out the details of a legal distribution scheme that would effectively result in "harm reduction", why bother? Davies was wasting his breath, Birt his paper - as I am wasting yours. I cannot imagine a rational, pragmatic approach to drugs in the western world evolving in my lifetime. Davies's proposal was sane, it was welcome; it was also self-destructive. Fellow Lib Dems rushed to clarify that he was not promoting party policy. And these are Lib Dems! Can you envisage an American presidential candidate going out on a limb to advocate that the US decriminalises heroin? That's right, with pigs flying merrily overhead, and hell freezing below.