For more than 50 years, the U.S. Drug Enforcement Administration (DEA) has been locked in a high-stakes contest with Mexican drug cartels. From the outside, that battle can look like a simple game of cat and mouse: agents versus smugglers, raids versus tunnels, seizures versus shipments. In reality, it is a shifting chess match, and recent marijuana legalization in many U.S. states has quietly changed the board.

Traditionally, cartels such as Sinaloa and Jalisco New Generation made billions growing low-cost cannabis in Mexico and moving it north through clandestine routes. DEA and other U.S. agencies responded with what’s often called the “kingpin strategy”—targeting cartel leaders, key lieutenants, and cross-border distribution networks with long-term investigations and joint operations with Mexican authorities.

As state-level marijuana reform spread after 2012, the basic economics began to shift. Legal cannabis markets in places like Colorado, Washington, and later other states undercut Mexican marijuana on quality and price. Research by RAND and other policy groups suggested that widespread U.S. legalization could reduce cartels’ cannabis revenue, which earlier estimates placed at a fraction of their total income but still a meaningful slice.

There is evidence that this is what happened. A binational study supported by Justice in Mexico found that as U.S. states legalized cannabis, seizures at the border and in Mexico dropped sharply, indicating less Mexican marijuana being smuggled north. Analysts note that legal U.S. producers now supply most of the domestic cannabis market, leaving cartels with a shrinking share.

But the DEA’s job hasn’t gotten easier—it has changed. Rather than giving up, cartels pivoted. Marijuana had already been losing ground to more profitable products, and legalization sped up that transition. Cartel organizations have reoriented their business toward synthetic drugs like methamphetamine and, most dangerously, illicit fentanyl, often using precursor chemicals shipped from China. These substances are easier to conceal than bulky bales of cannabis, more potent by weight, and generate higher profits.

The DEA’s current battle with cartels reflects this reality. Recent National Drug Threat Assessments emphasize that Mexican cartels remain the primary source of fentanyl, heroin, and meth in the U.S., and that these drugs, not marijuana, now drive overdose deaths and cartel profits. The agency has expanded bilateral operations, financial investigations, and targeting of “gatekeepers” who control smuggling corridors and money-laundering networks—an approach visible in initiatives such as Project Portero and U.S. efforts to dismantle cartel infrastructure and sanction cartel financiers.

So has marijuana legalization weakened the cartels? Yes, but in a narrow way. Legal state markets have cut into one of their older revenue streams, and lower cannabis profits mean fewer incentives to grow outdoor fields or move low-margin product across a heavily policed border. At the same time, analysts warn that legalization alone cannot “solve” the cartel problem because marijuana now represents a smaller share of their diversified portfolio.

For the DEA, the lesson is that drug policy and enforcement are inseparable. State-level cannabis reforms show how consumer behavior and regulation can reshape cartel business models. They also underscore the need for parallel strategies: stronger controls on precursor chemicals, smarter financial surveillance, better cooperation with Mexico, and demand-side investments in treatment and prevention.

In that sense, the evolving legality of marijuana is less a victory lap and more a case study. It shows that taking one product out of the black market can hurt organized crime—yet cartels will chase the next profitable drug unless broader public health and law-enforcement strategies evolve alongside them.