Rafael Caro Quintero, a suspected drug cartel leader, pleaded not guilty in a U.S. court on Friday to drug trafficking charges that could result in his execution.

Caro Quintero spent 28 years in prison in Mexico for the 1985 murder of former DEA agent Enrique “Kiki” Camarena. He was released in 2013 on a technicality, but was recaptured by Mexican authorities in 2022. He was indicted in absentia in 2020 in Brooklyn on drug trafficking and weapons charges.

Caro Quintero was extradited to the United States on Thursday as part of the biggest handover of suspected cartel members in years. He appeared in a large ceremonial courtroom packed with more than 100 DEA agents and was led toward the defense table by U.S. marshals, his wrists shackled with the same handcuffs Camarena once carried.

His lawyer, Michael Vitaliano, entered the not guilty plea on his behalf. U.S. Magistrate Judge Robert Levy ordered him detained pending trial.

Mexico’s surprise handover on Thursday of 29 alleged kingpins came amid President Donald Trump’s threats to order 25% tariffs on Mexican goods starting on March 4 over slow progress on stemming fentanyl as well as U.S.-bound migrant flows.

Lawyers for many of the defendants accuse the Mexican government of violating their rights with the forced U.S. transfer, since Mexican law mandates that its citizens can only be extradited to face charges in another country if they can be guaranteed not to face the death penalty.

Mexico’s Attorney General Alejandro Gertz on Friday said the transfer was legal under Mexico’s national security law. He said Mexico’s prohibition on the death penalty should be respected by other countries.

Questions over the legality of Mexico’s transfer will not affect Caro Quintero’s case in the United States, legal experts said, due to a 1992 U.S. Supreme Court case finding a Mexican national who was kidnapped and brought north could stand trial even though the U.S.-Mexico extradition treaty was not followed.

Thursday’s mass transfer featured mostly aging gang leaders such as Caro Quintero, co-founder of the Guadalajara Cartel, who reigned over Mexico’s criminal underworld decades ago.

Some of those handed over were younger suspected cartel members allegedly responsible for deadly shipments of fentanyl, a highly addictive synthetic opioid that has caused nearly half a million U.S. overdose deaths the past decade.

Some other drug lords likely continued to run criminal rackets from behind bars, according to security analysts, but Mexico’s volatile gangland leadership has mostly moved on.