Like those generals who used to discover that nuclear weapons were not a good thing about twenty minutes after they took off their uniforms and started collecting their pensions, we have had a parade of former presidents who knew that the war on drugs was a bad thing – but only mentioned it after they were already ex-presidents. Now, at last, we have one who is saying it out loud while he is still in office.

President Juan Manuel Santos of Colombia, the country that has suffered even more than Mexico from the drug wars, is an honest and serious man. He is also very brave, because any political leader who advocates the legalization of narcotic drugs will become a prime target of the prohibition industry. He has chosen to do it anyway.

“We are basically still thinking within the same framework as we have done for the past forty years,” he told “The Observer” in a recent interview in Bogota. “A new approach should try and take away the violent profit that comes with drug trafficking....If that means legalizing [drugs]...then I will welcome it.”

Santos has no intention of becoming a kamikaze politician: “What I won’t do is become the vanguard of that movement [to legalize drugs] because then I will be crucified. But I would gladly participate in those discussions, because we are the country that’s still suffering most...from the high consumption in the US, the UK and Europe in general.”

There are no such discussions, of course. Santos is being disingenuous about this; he is really trying to start a serious international debate on drug legalization, not to join one. But the time may be ripe for such a debate, because it is now almost universally acknowledged (outside of political circles) that the “war on drugs” has been an extremely bloody failure.

Twenty years ago Milton Friedman, a Nobel Prize winner, the most influential economist of the 20th century, and an icon of the right, said: “If you look at the drug war from a purely economic point of view, the role of the government is to protect the drug cartel.” It is only because the government makes the drugs illegal that the criminal cartel has a highly profitable monopoly on meeting the demand.

Milton Friedman also said: “Government never has any right to interfere with an individual for that individual’s own good. The case for prohibiting drugs is exactly as strong and as weak as the case for prohibiting people from over-eating. We all know that over-eating causes more deaths than drugs do.” But there are a quarter-million Americans in jail for possessing or selling drugs. Nobody is in jail for producing, marketing or eating junk food.

Friedman was right, of course, but forty years of the war on drugs have also shown that arguments based on logic, natural justice, or history (the obvious parallel with alcohol prohibition in the US in the 1920s and early 30s) have very little effect on policy in the main drug-importing nations. Many politicians there know that the war on drugs is futile and stupid, but the political cost of leaving the herd and saying so out loud is too high.

The political leaders who are starting to say that it’s time to end the war and legalize the drugs are almost all in the producer nations, where the damage has been far graver than in the drug-importing countries. In practice, therefore, they are almost all Latin American leaders – but even there they have waited until they left office to make their views known.

Former Mexican president Vicente Fox supported the US-led war on drugs when he was in office in 2000-2006, but more recently he has condemned it as an unmitigated disaster. “We should consider legalizing the production, sale and distribution of drugs,” he wrote on his blog. “Radical prohibition strategies have never worked.”

“Legalization does not mean that drugs are good,” Fox added, “but we have to see it as a strategy to weaken and break the economic system that allows cartels to make huge profits, which in turn increases their power and capacity to corrupt.”

Naturally, Fox only said all that when he was no longer president, because otherwise the United States would have punished Mexico severely for stepping out of line. In the same spirit, former presidents Fernando Henrique Cardoso of Brazil, Cesar Gaviria of Colombia and Ernesto Zedillo of Mexico made a joint public statement that drug prohibition had failed in 2009 – after they had all left office.

But gradually Latin American leaders are losing their fear of Washington. Last year Mexican President Felipe Calderon called for a debate on the legalization of the drug trade, although he carefully stressed that he himself was against the idea. (Then why did you bring it up, Felipe?) And now President Santos of Colombia has come out, still cautiously, to say that he would consider legalizing not only marijuana but cocaine.

The international discussion on legalization that Santos wants will not start tomorrow, or even next year, but common sense on drugs is finally getting the upper hand over ignorance, fear and dogmatism. And cash-strapped governments will eventually realize how much the balance sheet could be improved by taxing legalized drug consumption rather than wasting hundreds of billions in a futile attempt to reduce consumption.