Mexican President Claudia Sheinbaum wants to know the truth about how Ismael "El Mayo" Zambada, a top drug cartel leader, ended up in US custody. At a recent press briefing, she asked directly: "¿Quién mintió?" — who lied? Her question points to a disagreement that has simmered in Mexico City since Zambada was captured nearly two years ago in a way that Mexican officials still don't fully accept.

The Mexican government has formally asked the FBI to explain whether it took part in the operation that brought Zambada to the United States. At the same time, Mexico's federal Attorney General's Office (known by its Spanish acronym FGR) has opened new investigations to figure out whether American law enforcement agents worked on Mexican territory without permission. Investigators have now identified the exact location where Zambada and two others were held, which is important evidence for any legal case Mexico might build.

A capture that nobody agrees on

When Zambada arrived in the United States in late July 2024, American officials called it a major win: an elderly leader of the Sinaloa Cartel brought in safely and without gunfire. But the way it happened—Zambada was reportedly tricked onto a plane and flown to New Mexico rather than going through normal extradition procedures—meant Mexican officials were left out of the loop. Sheinbaum's predecessor voiced concern that the operation broke Mexican law. Sheinbaum has now made that concern official by demanding answers from Washington.

Zambada first said he was not guilty of drug trafficking charges in a Texas court on July 26, 2024. But over time, his stance changed. By February 2025, his lawyer said he wanted to make a deal to avoid the death penalty. In August 2025, Zambada changed his mind again and pleaded guilty in US federal court.

The guilty plea solved the case in the United States, but it opened a new problem in Mexico. When Zambada admits guilt in a Texas courtroom, it settles the drug charges against him. But it does nothing to answer Mexico's real question: Did the way he was captured break Mexican law? Did American law enforcement officers work on Mexican soil without permission?

Why Mexico is asking these questions now

The timing is important. Now that Zambada has pleaded guilty and his US case is closed, Mexican authorities can investigate whether the capture was legal without worrying that their findings might affect his American prosecution. The fact that Mexican investigators have found the exact place where Zambada was held gives them a solid piece of evidence to build a case around unlawful kidnapping—something they could use against US officials diplomatically, even if no American is ever tried in Mexico.

When Sheinbaum asks who lied, she could be pointing at three possibilities: American agencies that misled Mexican officials about the operation, Mexican officials who knew more than they admitted publicly, or cartel members who moved Zambada without either government knowing. Mexican officials haven't said which one they think is true, and that unclear position actually helps Sheinbaum, because it lets her demand answers from Washington without blaming anyone yet.

This argument is happening while the US and Mexico are already struggling to work together on security. Both countries are dealing with drugs, trade threats, and military questions all at the same time. Mexico's formal demand for FBI answers, plus a government investigation, adds another layer of tension at a moment when Mexico doesn't have much power to make the US do anything. So far, the United States hasn't publicly responded to Mexico's request.

What happens next depends on whether Washington cares more about keeping this dispute quiet or about protecting secrets about how Zambada was actually captured. That choice will shape how these two countries work together on security for a long time.