Mexican President Claudia Sheinbaum has publicly demanded clarity on the FBI's role in the 2024 capture of Sinaloa Cartel co-founder Ismael "El Mayo" Zambada, asking directly: "¿Quién mintió?" — who lied? Her question, posed at a recent press briefing, brings into focus a dispute that has existed in Mexico City since Zambada turned up in US custody nearly two years ago under circumstances Mexican officials have never fully accepted.

The Mexican government has formally requested that the FBI explain its possible participation in the operation that delivered Zambada to American soil. In parallel, Mexico's Fiscalía General de la República (FGR) — the federal Attorney General's Office — has opened new investigations specifically examining whether US federal agents took part in what Mexican authorities characterize as an unauthorized cross-border operation. Investigators have already identified the physical location where Zambada and two associates were deprived of their liberty, a key piece of evidence for any Mexican case around unlawful abduction.

A capture without an agreed explanation

Zambada's arrival in the United States in late July 2024 was framed by US authorities as a major victory: the octogenarian co-founder of the Sinaloa Cartel, alongside Joaquín "El Chapo" Guzmán, brought into custody without violence. But the method—reportedly lured onto a plane and flown into New Mexico rather than extradited through standard legal channels—left Mexican officials sidelined and, by their account, uninformed beforehand. Sheinbaum's predecessor, Andrés Manuel López Obrador, voiced early concern about whether the operation respected Mexican sovereignty. Sheinbaum has now turned that concern into a formal bilateral demand.

Zambada initially pleaded not guilty to drug trafficking charges in a federal court in Texas on July 26, 2024. That stance shifted over time. By February 2025, his attorney indicated Zambada was seeking a plea agreement to avoid the death penalty. In mid-August 2025, reporting suggested the plea was imminent, and on August 25, 2025, Zambada formally reversed course, entering a guilty plea in US federal court.

The guilty plea resolved the American legal chapter of the case but opened—rather than closed—the Mexican one. A guilty plea in a Texas courtroom addresses the trafficking charges against Zambada. It does nothing to resolve the question Mexican prosecutors are pursuing: whether the operation that placed Zambada in US hands violated Mexican law, and whether foreign law enforcement personnel operated on Mexican territory without proper authorization under existing bilateral agreements.

Why Mexico's new investigation gains urgency now

The timing matters. With Zambada's US prosecution concluded by plea, Mexican authorities are no longer concerned that domestic findings could complicate an active American case. The FGR's identification of the site where Zambada was held gives Mexican investigators a concrete location for building a case around unlawful deprivation of liberty—a charge that, if substantiated against US personnel, would carry diplomatic weight even if no American ever faced trial in Mexico.

Sheinbaum's question—who lied—points in at least three directions: US agencies that may have misrepresented the operation to their Mexican counterparts, Mexican officials who may have known more than they disclosed publicly, or intermediaries within the cartel who orchestrated Zambada's movements outside either government's full knowledge. Mexican officials have not specified which they believe most likely, and the ambiguity itself serves a political purpose, allowing Sheinbaum to press Washington for clarity while avoiding blame that could strain the broader security relationship.

This dispute is unfolding within a US-Mexico security partnership that has become more transactional and less collaborative in recent years. Both governments are negotiating fentanyl interdiction, tariff threats, and troop deployment questions on separate tracks. A formal Mexican demand for FBI clarification, backed by an active FGR investigation, adds a sovereignty concern to that mix at a moment when Mexico has limited leverage to force a substantive US response. Washington has not, according to available reporting, issued a public reply to Mexico's request.

Whether the FBI or any other US agency responds substantively to Mexico's inquiry will likely turn on how much diplomatic cost Washington assigns to the dispute versus the operational value it places on shielding details of how a cartel figure of Zambada's stature was actually brought into custody. That calculation remains unresolved and, in some form, will shape US-Mexico relations on security matters going forward.