Rounding up the killers of U.S. Immigration and Customs Enforcement officer Jaime Zapata will not curtail Americans’ voracious appetite for mind-altering substances.The murder of U.S. Immigration and Customs Enforcement officer Jaime Zapata in the state of San Luis Potosí on Feb. 15 shocked and outraged the American law-enforcement community. For Mexican law enforcement it was just another day at the office.Early indications are that Zapata was killed by members of the Mexican drug cartel known as the Zetas. If so, his death adds to a shocking statistic. The latest data available from the Mexican government show that 87 members of the Mexican military and 867 law- enforcement officers were killed by drug gangs between December 2006, when President Felipe Calderón took office, and March 2009. Undoubtedly the number is higher now.Around 35,000 Mexicans are known to have died in drug- related violence since December 2006—15,273 of those just last year. To understand the magnitude of this violence, consider that the per capita equivalent for the U.S. would be some 98,000 dead.While Mexico’s 18 murders per 100,000 in 2009 is still well below the rate in Colombia (35) and Guatemala (52), it is a lot higher than it was in 2007 (eight) and a lot higher than in the U.S. in 2009 (five). It represents a sharp reversal of a improving trend after 1999. American demand for illegal narcotics—the source of this escalating violence—meanwhile shows no sign of letting up.It is not unreasonable to suggest that if the U.S. was facing similar rates of bloodshed, Washington would be forced to reconsider the wisdom of its prohibition approach to the narcotics business. But the suffering is south of the border, out of sight and out of mind for Americans and, therefore, their politicians. Meanwhile, a multi-billion dollar U.S. bureaucracy dedicated to fighting this war has little incentive to see it won or change course.The prospects for “victory” appear increasingly dim. The trouble is that the rule of law in any free society emanates from the norms and values of the culture. When it comes to voluntary transactions between two parties, the government may pronounce one thing but if the population doesn’t share that view, it will not abide by the law.Exhibit A is America’s robust recreational drug culture, easily observable in television, film and the arts. The July 2008 Science Daily reported on a study at Australia’s University of New South Wales using statistics produced by the World Health Organization. It found that the U.S had the highest levels of cocaine and cannabis use among 17 countries studied. The authors said that some “16.2% of people in the U.S. had used cocaine in their lifetime, a level much higher than any other country surveyed (the second highest level of cocaine use was in New Zealand, where 4.3% of people reported having used cocaine).” U.S. cannabis use topped 42%.It is Mexico’s bad luck to sit next to this lucrative drug market. And it doesn’t help that once the drugs are over the border they seem to reach consumers with ease. As Juarez’s then-mayor-elect Héctor Murguía told me in an interview at his home last fall: “We need to ask the U.S. how you have a calm country despite the high rate of consumption.” Or to put it less delicately, perhaps the capos risk it all at the border because they know that from McAllen, on the Texas border, to Seattle, they’re home free. It’s hardly a surprise that raids by feds last week to hunt down Zapata’s killers netted 676 cartel suspects in the U.S.Mexico has tried to rationalize the casualty toll by arguing that 85% of the dead were gangsters killed by rival cartels. But with over 90% of the murders in Juarez (where 3,100 were killed last year) unsolved, it is hard to see how such a statement can be made. What is more, tens of thousands of vulnerable children have been recruited to work in the business, and some of them get killed too. Their deaths as cartel fodder cannot be shrugged off. Finally, even if the government’s numbers are right, we’re left with 5,250 innocent victims, a number far too large to write off as collateral damage.Why should Mexicans be asked to give their lives because Americans have a voracious appetite for mind-altering substances? Mr. Calderón has done little to elevate this question. Instead he claims the war is justified because consumption is now an issue at home. But Mexico’s data do not support this, as former foreign minister Jorge Castañeda wrote in a May 6, 2010 paper for the Cato Institute: “‘Users of drugs have gone up from 307,000 to 465,000 over the last seven years (2002—2008), which in a country of 110 million people, is not a huge drug problem.”