Bernd Debusmann- Bernd Debusmann is a Reuters columnist. The opinions expressed are his own -There are times when silence can be as eloquent as words. Take the case of Washington's reaction to announcements, in quick succession, from Mexico and Argentina of changes in their drug policies that run counter to America's own rigidly prohibitionist federal laws. No U.S. expressions of dismay or alarm.Contrast that with three years ago, when Mexico was close to enacting timid reforms almost identical to those that became effective on August 21. In 2006, shouts of shock and horror from the administration of George W. Bush reached such a pitch that the then Mexican president, Vicente Fox, abruptly vetoed a bill his own party had written and he had supported.What has changed? Was it a matter of something happening in August, when most of official Washington is on holiday? Or was it a sign of greater American readiness to rethink a war on drugs that has, in almost four decades, failed to curb production and stifle consumption of illicit drugs? And that despite law enforcement efforts that resulted in an average of around 4,700 arrests for drug offences every single day since the beginning of the millennium. (Just under 40 percent of those arrests are for possession of marijuana).Or was it a matter of more countries realising that, as drug reform advocate Ethan Nadelmann puts it, "looking to the United States as a role model for drug control is like looking to apartheid-era South Africa for how to deal with race." Nadelmann heads the Drug Policy Alliance, one of several groups lobbying for reform of U.S. drug policies.Under the Mexican law that took effect in August, it is legal to possess small, precisely specified amounts, for personal use, of  marijuana, heroin, opium, cocaine, methamphetamine and LSD. In Argentina, the Supreme Court declared unconstitutional criminal sanctions for the possession of small quantities of marijuana for personal use. The ruling opened the door to legislation similar to Mexico's.Brazil decriminalised drug possession in 2006; Ecuador is likely to follow suit this year. In much of Europe, drug use (as opposed to drug trafficking) is treated as an administrative offence rather than a criminal act. America's hard-line approach has helped to make the United States the country with the world's largest prison population.Advocates of more flexible policies say they feel the winds of change beginning to rise in the administration of  Barack Obama, a president who has admitted that in his youth, he smoked marijuana frequently and used "a little blow"(of cocaine) when he could afford it. But hopes for a break from long-standing orthodoxy might be premature, even though a recent Zogby poll showed 52 percent support for treating marijuana as a legal, taxed and regulated drug.AMSTERDAM'S SCHIZOPHRENIC PRAGMATISM "As regards to legalization, it is not in the president's vocabulary and it is not in mine," Obama's drug czar, former Seattle police chief Gil Kerlikowske said in July. "Marijuana is dangerous and has no medicinal benefits."Oddly, he made the statement in California, where an estimated 250,000 people can legally buy marijuana with a letter of recommendation from their physician. The drug is used for a variety of illnesses, from chronic pain to insomnia and depression. There is extensive academic literature on the medical benefits of marijuana.Medical opinion, however, conflicts with the congressionally-mandated job description Kerlikowske inherited when he took up the post. It says that the director of the Office of National Drug Policy, the White House group in charge of drug war strategy, must "oppose any attempt to legalize the use of a substance listed in schedule I of section 202 of the Controlled Substances Act."Schedule I of the act, which took force in 1970 during the administration of Richard Nixon, the president who formally declared "war on drugs", places marijuana alongside powerfully addictive drugs such as heroin. The wrong-headed classification matches that of an international treaty, the 1961 United Nations Single Convention of Narcotics Drugs. The convention is a major obstacle for signatory countries that want to legalize drugs.No country has actually done that. Even the Netherlands, the Mecca of marijuana aficionados, operates on a system best described as schizophrenic pragmatism. Amsterdam's "coffee shops" are allowed to have 500 grams of marijuana on the premises and sell no more than 5 grams per person to people over 18. The runners who re-supply the shops routinely carry more than the legal quantity and violate the law. So do importers.While the failure of the drug war and the prohibitionist ideology that drives it have been analysed in great detail in scores of sober assessments by academics and government commissions, there have been few studies of the "how to" of legalization. What, for example, would happen to the criminal mafias that are now running a violent illicit business with a turnover estimated at more than $300 billion a year?Some drug traffickers would switch to other criminal activities and it is realistic to expect increases in such areas as cyber crime and extortion, according to Steve Rolles, Head of Research of the Transform Drug Policy Foundation, a British think tank. "But the big picture will undoubtedly show a significant net fall in overall criminal activity in the longer term," he said in an interview. "Getting rid of illegal drug markets is about reducing opportunities for crime."Rolles is author of the optimistically titled "After the war on drugs: Blueprint for Regulation," a book scheduled for publication in November and meant to kickstart a debate on what he sees as something of a blank slate - the specifics of regulation for currently illegal drugs.On a global scale, nothing much can happen unless there are changes in the world's largest and most lucrative market for drugs, the United States. If they happen, they won't happen fast. "I see this as a multi-generational effort, with incremental changes," said Nadelmann, who has been involved in drug policy since he taught at Princeton University in the late 1980s. "But for the first time, I feel I have the wind in my back and not in my face."(You can contact the author at Debusmann@Reuters.com)