Former Gulf Cartel leader Osiel Cardenas released from U.S. prison after over a decade

The United States has released Osiel Cardenas Guillen, former leader of the Gulf Cartel and founder of the Zetas, an armed organization that played a salient role in violent turf wars that marked Mexico over the past decades.

Cardenas had been captured in Mexico in 2003 and extradited to the U.S. four years later, where he was accused of "overseeing a vast drug-trafficking empire responsible for the import of thousands of kilos of cocaine and marijuana to the U.S. from Mexico."

He pleaded guilty to several grave charges pressed against him, including conspiracy to own and distribute controlled substances, as well as money laundering, and received a 25-year sentence in 2010. He also had to pay $50 million in the U.S. due to his "illegal activities." But now, 14 years later, he has been released.

The former drug lord still has pending accusations in Mexico, but U.S. authorities have yet to decide whether to extradite him or keep him in the country under parole.

While still free, Cardenas was among the most powerful drug lords in Mexico. He oversaw a large marijuana and cocaine trafficking ring rivaling enterprises such as the Sinaloa Cartel. Based in the border state of Tamaulipas, it mainly used its 370-kilometer long border with Texas to smuggle drugs into the U.S.

But according to specialized outlet InSight crime, his most significant legacy was the creation of the Zetas, an "armed force made of deserters from an elite unit of the Mexican army." This group, it added, "professionalized Mexico's gangland warfare by detonating an arms race and introducing a kind of brutal violence never before seen in the country."

The outlet added that Cardenas doesn't seem to have remaining links to the Gulf Cartel, which has split into smaller groups since he was imprisoned.