Colombia’s new president, Gustavo Petro, wants to legalize and regulate cocaine in his country. He is correct that prohibition in South America, driven by billions of dollars of American aid, is ineffective and wasteful. Still, Mr. Petro’s scheme to legalize cocaine unilaterally will not curb violence and corruption fueled by illicit international trafficking, and it might inadvertently create more problems than it solves. The U.S. should listen to the will of Colombia’s people and help find an option somewhere between failed enforcement and heedless legality.    

The domestic cocaine market in Colombia accounts for little of the profit, and thus little of the violence and corruption associated with the drug. Though the country decriminalized cocaine possession, the use rate in Colombia is less than half of that in the United States. Rather than eke out a living by selling cocaine for a few dollars per gram domestically, most manufacturers send their products to more affluent countries, where demand is much higher. Under Mr. Petro’s plan, regulated cocaine producers will still be excluded from lucrative international markets, so manufacturers would have little additional incentive to shift their focus and operate lawfully within the industry. A legal domestic market would be small and unprofitable, and its existence would solve none of the truly harmful problems cocaine production creates. 

Even if a domestic market were viable, Mr. Petro’s government could not guarantee its competitiveness against existing criminal networks. Illegal drug markets do not simply disappear when a legal market is declared, as Felipe Tascón, Colombia’s drug czar, has suggested. Rather, legal markets and recalcitrant illicit markets can coexist for years, as experiments with cannabis liberalization in some U.S. states have proven. As such, to prevent unlicensed sellers from undercutting the authorized regime, robust enforcement must continue. If, through hasty legalization, Mr. Petro’s government alienates the U.S. and other international backers who have long bankrolled the country’s drug enforcement agencies, it may have to foot the bill. 

If cocaine regulation does lower the price sufficiently to stimulate domestic demand over time, it could also create a public health crisis. Cheaper, more prevalent cocaine could eventually swell abuse rates, particularly among people with low socioeconomic status. Crack and basuco, an inhalant derived from the toxic byproducts of cocaine production that causes dependence among 6 out of 10 users, are even more worrisome. Efforts at anti-drug prevention among teenagers and young adults in Colombia, long based on debunked American programs, have largely been ineffective. Treatment is scarce for most Colombians and, when available, rarely utilized. After legalization, Mr. Petro’s government must add the costs of public health mitigation to its growing list of expenses. 

As misguided as sudden legalization would be, the U.S. has room to negotiate. Importantly, some of Mr. Petro’s aims, such as an end to the eradication of coca farms, would not threaten U.S. interests. Because the supply and price of cocaine in the U.S. reflect the costs to maintain illicit international supply chains more than the costs of illicit production, they would not change even if Colombian production were to rise. The most reliable indicators of drug abuse, such as treatment admissions and workplace urinalysis screening results, have not changed significantly with fluctuations in cocaine production. Recent increases in overdose rates are likely driven more by co-occurring opioids than increased availability of cocaine. Spillover from surplus legal producers to other countries is possible but unlikely to change the amount of cocaine consumed outside Colombia. Still, to retain the financial support of Colombia’s allies, Mr. Petro’s government must convince them that a domestic legal market can and will remain contained. He is more likely to do so through incremental rather than abrupt change. 

For a country that considers cocaine use a fundamental human right, legalization given proper guardrails is not unreasonable. Still, Colombia cannot afford to do it alone without creating costs that exceed benefits. A regulated cocaine market in Colombia need not threaten U.S. public health and safety. Instead of trying to stonewall it, we should work with Colombia’s government to help develop prevention and treatment for drug users, stop the spillover of cocaine to other countries, and refocus enforcement on people with guns rather than people with tractors. Mr. Petro’s statement, much like his mandate, is a wake-up call to U.S. leaders that if we do not help Latin American governments fight crime on their terms, they might go it alone, with dangerous results for their people and prolonged costs to American taxpayers.