Imagine it’s 1983, and you’re a drug dealer working for Mexico’s Sinaloa Cartel, the world’s most powerful drug trafficking syndicate. As a member of the cartel, it’s your job to oversee the production of marijuana in a 1500 square foot house near the syndicate’s headquarter city of Culiacan, Mexico. After only three months of growing, you’re ready to harvest a house-full of weed, at a production cost of about $300 per pound (in 2010 dollars). Once you harvest, members of your cartel will move your product to the United States–murdering, torturing, and terrorizing all the way.

Why send the product all the way to the U.S.? Remember, it’s 1983, and weed prices are skyrocketing thanks to the Reagan administration’s War on Drugs. In California, the Reagan administration just launched a massive campaign to lock up the marijuana growers, which has shrunk the weed supply and caused prices to skyrocket to $5,000 per pound–a 1,600% profit for you and your criminal organization.

Fast forward to today, in which marijuana has “legal and quasi-legal protections in more than two dozen U.S. states.” It’s a different story. Your marijuana is reaping a lot less profit as it competes with better quality domestic weed in the American market. As a Mexican marijuana grower, you find yourself wishing for the good ol’ days when Reagan was fighting a war on drugs, spending billions to keep your profits high.

The lesson here is simple: Criminalizing marijuana use and production creates a dangerous and unregulated industry, where the worst of the worst reap enormous profits. Drug cartels have killed more than 60,000 people in Mexico from 2006 to 2012, and they’ve used billions of dollars of profits from illegal drug sales to do it.

Cartels make about a fifth of their profits from marijuana sales, so there’s no doubt that US decriminalization of marijuana on a federal level would do some damage to cartel profits. Beau Kilmer, the co-director of the RAND Drug Policy Research Center, confirms that “driving Mexican marijuana out of the U.S. would probably reduce the traffickers’ export revenue by a few billion dollars a year.”

Whether that will reduce violence or contribute to ending drug crime in Mexico is another question. This largely depends on what types of drugs replace marijuana, and whether those drugs are easy to combat.

As weed profits for the cartels fall, Mexican traffickers are now sending heroin and methamphetamine across the U.S. border, the latest drug seizure statistics show. As reported in the Washington Post, “U.S. law enforcement agents seized 2,181 kilograms of heroin last year coming from Mexico, nearly three times the amount confiscated in 2009.” Meth confiscations have risen even more dramatically: “Last year, 15,803 kilograms of the drug was seized along the border, up from 3,076 kilos in 2009.” This rise in the movement of meth and heroin across the border is correlated with a 37 percent decrease in the amount of marijuana seized by border officials since 2011.

This development may sound scary. Now that heroin and meth are flooding across the border, have we created a greater threat by decriminalizing weed in many states?

There are reasons to be optimistic. For one, it’s probable that Mexican heroin and meth producers are simply outcompeting American ones–replacing them, not joining them. The National Institute on Drug Abuse reports “no statistically significant changes” in American meth and heroin abuse from 2011 to 2013, during the time border officials have seen enormous spikes in movement of those drugs across the border.

Moreover, there’s simply a smaller consumer base for hard drugs like heroin and meth. There are about 600,000 regular heroin users in the United States, and about 440,000 regular methamphetamine users. Compare that with the estimated 10-20 million regular weed smokers in the United States, and the cartels’ switch to heroin and meth doesn’t seem very profitable.

Meth production also may be easier than marijuana for the Mexican government to regulate and possibly even eliminate. This is because meth is produced using chemicals obtained legally, such as cleaning chemicals. The United States has generally effective methods of preventing these “precursor chemicals” from being obtained in large amounts by drug producers, but the Mexican government has yet to enact such measures. If Mexico follows the U.S.’s policies by tightening regulations, meth production would be more difficult.

The important thing to remember is that decriminalizing marijuana means bringing one of the biggest and most dangerous illegal markets out of the shadow economy. It takes profits out of the hands of violent criminal organizations. Decriminalizing marijuana won’t end drug crime in Mexico, but it will cost drug cartels billions.

Contact Cory Herro at cherro ‘at’ stanford.edu.