A Mexican court on Friday freed notorious drug kingpin Rafael Caro Quintero, who was convicted of ordering the killing of a U.S. Drug Enforcement Administration officer in 1985.
Caro Quintero was freed after the court decided he should have been tried at a state level, rather than federal level, a court official said, ending his 28-year stay behind bars.
"There are various factors, and among them the fact that he already served his time for drug trafficking," the court official said.
He was released from the Puente Grande prison in the western Mexican state of Jalisco on Friday morning, according to the state attorney general's office.
Caro Quintero, who is believed to be in his 60s, holds a special place in Mexican drug lore and was one of the leaders of the Guadalajara cartel, a forerunner of the Sinaloa cartel which is currently led by Joaquin "Shorty" Guzman, the country's most-wanted drug lord.
Caro Quintero was convicted of ordering the 1985 kidnapping, torture and murder of Enrique Camarena, an undercover DEA agent behind a number of successful drug busts.
At the time, the United States expressed anger at a perceived lackluster effort to catch Camarena's killer and the episode marked a low point in Mexico-U.S. relations. Caro Quintero was caught in Costa Rica in 1985.
According to a source from the Mexican attorney general's office, Caro Quintero cannot be extradited to the United States because a decision by Mexico's Supreme Court bars extradition of Mexicans to countries that may impose the death penalty or life imprisonment - punishments excluded by Mexican law.
A spokeswoman for the U.S. Department of Justice declined to comment on whether the United States would seek his extradition.
More than 70,000 people have been killed in drug-related killings in Mexico since 2007 when the government launched a militarized attack on the warring cartels.
President Enrique Pena Nieto, who took office in December, has shifted the focus away from going after cartel bosses to tackling violent crimes such as extortion and kidnapping.