By Adam Siegel

Colombian president Juan Manuel Santos is likely to open the Sixth Summit of the Americas in Cartagena next month with a standard welcome for Barack Obama and the 33 other leaders of the Western Hemisphere, but maybe there's a more fitting greeting for the U.S. president: "This is an intervention." After decades of partnering with the U.S. to pursue an aggressive, often controversial 'war on drugs,' a number of Latin American leaders say they're ready to discuss major shifts in regional anti-drug policy. Some of them have begun talk of "decriminalization" -- and they want to do it at the Summit, where the United States will have no choice but to talk up the merits of the prohibition policies it has long favored.

The former presidents of Brazil, Colombia, and Mexico generated headlines in 2009 by jointly declaring that "the war on drugs has failed" and calling for decriminalization of marijuana, but the commentary was dismissed in some quarters as an easy argument to make for men no longer politically accountable as heads of state. Since then, however, several sitting Latin American leaders (on both the left and right) have called for candid debate of current drug policy. Among them: Mexico's Felipe Calderon, Costa Rica's Laura Chinchilla, Argentina's Cristina Kirchner, Guatemala's Otto Perez Molina, and Colombia's Santos -- who told Britain's The Observer last year that "A new approach should try and take away the violent profit that comes with drug trafficking... If that means legalizing, and the world thinks that's the solution, I will welcome it."

Santos' caveat -- "[if] the world thinks that's the solution" -- nods to the global reach of Latin America's drug trafficking organizations, underscoring the desire for a debate that includes producers and consumers (who are concentrated in the U.S. and Europe). This distinction is important; indeed, personal consumption of drugs like marijuana and cocaine is already technically decriminalized in Mexico, Costa Rica, and Colombia, while the total number of convictions for personal drug possession in Guatemala and Argentina combined was just 161 in 2009, according to the Inter-American Drug Abuse Control Commission. So when an ex-military general like Perez or a former defense minister like Santos talks about decriminalization, it's not because they care so much about personal liberties. Rather, they have one major goal in mind: choking off the resources that fuel drug cartels and the violence they practice.

As Perez explained recently in advance of a Central American conference on alternative drug strategy sponsored by his administration in Antigua, "drugs are expensive precisely because they are prohibited...traffickers will lose if they cease to be profitable." While no detailed proposal is yet on the table, his idea of decriminalization is clear: create a legal framework to make the production and transport of cocaine legal, at least throughout Central America -- a region through which approximately 80 percent of the cocaine heading to the United States stops. Bringing the business of this $37 billion industry out into the open, it is assumed, would reduce the imperative of traffickers to corrupt public officials and their need to use violence against both governments and rivals for access to the best trafficking routes.

Other leaders, from Vice President Joe Biden to Nicaraguan president Daniel Ortega, have rejected the decriminalization proposals out of hand. Nevertheless, the coordinator of Obama's trip to Colombia recently indicated that the U.S. was "ready to have a good dialogue between all countries to hear their views," though he reiterated that U.S. opposition to any legalization will not change. Of the suggestions offered at the Guatemala conference last weekend, some could be endorsed by the U.S. -- such as the creation of a regional Central American court for trying traffickers that would reduce local corruption and relieve pressure on national justice systems, while others -- mandating that the U.S. take "co-responsibility" and pay individual countries for every drug raid or plant eradicated -- don't stand a chance.

Obama's challenge at the Summit will be to offer policy alternatives to the status quo. Latin American leaders warn that Washington has asked them to take tough choices over the years, and they want to see the U.S. demonstrate the political courage to consider a few of their own. Latin Americans are far from united on decriminalization or any other single solution, but the gathering in Cartagena will make clear that they have become increasingly willing and able to propose new ideas they know that Washington won't like. If Guatemala's Perez Molina gets his way, we'll even see him start discussions on a formal drug transit corridor for moving cocaine between South America and the United States.

Wartime U.S. presidents talk often of the need to "listen to the generals on the ground." In coming years, beginning in Cartagena, Washington can expect its "frontline partners" in the war on drugs to offer up strategies and ideas that U.S. policymakers won't like. Some Latin American leaders may give Obama a break during an election year, but they aren't prepared to wait much longer.

Adam Siegel is a researcher in Eurasia Group's Latin America practice.