CARTAGENA DE INDIAS, Colombia—I imagined I would be able to find cocaine in Cartagena, Colombia’s famous Caribbean seaport. I just didn’t know how quickly, and how cheap it would be. It took me a five-minute evening drive from the Walled City to the Calle de la Media Luna, where dealers offer “perico” at every corner. The price? Twenty-thousand pesos ($8) for one gram. “Too pink for my taste,” I said, trying to appear dignified as I walked away. I had the information I needed for this column: Cocaine is abundant and cheap.

In Colombia, it takes only a few minutes to confirm what politicians across the Western Hemisphere fail to acknowledge publicly—that the drug war is a glorious failure. It also takes a few minutes to realize the devastation brought about by the mafias that owe their existence to the war on drugs. The day I arrived, the country was shocked by yet another death connected to a recent scandal relating to the links between one of the paramilitary groups and the political establishment. Jairo Andres Angarita, one of the bosses of a 35,000-member force demobilized in exchange for reduced sentences, was killed because he possessed information about meetings that took place in 2001 between well-known politicians and his right-wing paramilitary group known as United Self-Defense Forces of Colombia—a group funded, like its left-wing counterparts, by cocaine.

Since 2002, Alvaro Uribe’s government has made a colossal effort to combat coca cultivation, devoting one-third of annual U.S. assistance to that purpose. In the following three years, coca plantations dropped by between one-third and one-half. But growers moved from big plantations to small plots in virtually every state of the country, so the initial successes were eventually reversed. Most fields detected nowadays are new.

In a country that has made admirable progress on other fronts, the drug war is preventing the government from finishing off the narco-terrorist organizations. Between 2002 and 2005, Uribe’s “democratic security” policy successfully pushed those organizations, especially the Marxist empire known as FARC, away from many cities. There was a one-third drop in the number of murders and a two-thirds drop in the number of terrorist attacks. The economy picked up handsomely. But then a stalemate ensued in the campaign against the terrorists that cannot be attributed only to the country’s jungles. The mafias that owe their existence to the criminalization of cocaine continue to generate enough funds to match every attempt by the government to beef up its military capability.

The frustration is reopening the debate on the drug war. Some politicians are openly calling for decriminalization. Others propose intermediate mechanisms. Analyst Olga Gonzalez says that “in the last 15 years, hundreds of Colombians have been extradited to the United States and hundreds of thousands of hectares have been fumigated, and yet cocaine remains an excellent business. The link between mafias and politics has now reached the upper echelons of power, as the revelations of ‘para-politics’ show.” She recalls that Colombia had a lucrative marijuana trade in the 1970s. When Americans started to grow their own, the Colombian mafias disappeared. Why don’t American laboratories, she asks, continue to develop the synthetic cocaine for which there is already a prototype? Or why don’t Americans develop a genetically modified coca leaf needing less solar radiation and tropical humidity so that consumers can grow it in their balconies?

Actually, all of these solutions would face the barrier of prohibition at the consumer level. And in the case of synthetic cocaine, the real thing is much cheaper to produce—the drug war notwithstanding. The debate that needs to be addressed is the one about decriminalization. The place to open that debate is not Colombia but the United States. No Latin American government could decriminalize drugs unilaterally without incurring the fatal wrath of the United States, exposing its country to ferocious reprisals. A recent example is former Mexican President Vicente Fox’s attempt to sign into law a bill passed by Congress legalizing tiny amounts of certain drugs for personal consumption. When the seven plagues of Egypt fell upon Fox—courtesy of Washington—the conservative president was forced to rethink.

From time to time, a debate opens up in the United States about decriminalizing some drugs, but it quickly fades away. It is a sensitive matter because of the horrendous consequences linked to drug abuse. Still, well-known figures such as Henry Kissinger or the late Milton Friedman, and respected publications such as the Economist magazine, have argued for decriminalization. However well meaning, the U.S. war on drugs is doing much more harm than good to Colombia, one of America’s staunchest allies in the Western Hemisphere. That is something that merits reopening the debate sooner rather than later.