Villarreal, a former federal police officer who also goes by El Grande and King Kong, was first arrested in 2010, when Mexican marines captured him without a shot being fired during a raid outside of Mexico City in 2010. He was charged with multiple murders.
According to Univision, Thursday's extradition could indicate that Villarreal will become a protected witness for the U.S. Drug Enforcement Agency, and he has reportedly already testified against retired General Tomas Angeles Dauahare and General Roberto Dawe Gonzalez, who are currently being investigated for links to an unnamed drug cartel.
After his election in 2006, Mexico President Felipe Calderon began a military offensive against drug trafficking, and the Beltran Leyva cartel is perhaps Calderon's greatest victory in this war.
The gang's founder, Beltran Leyva, was killed by the Mexican navy in 2009, and subsequent in-fighting and arrests have effectively disbanded the once-powerful cartel, according to the BBC.
But Calderon's crackdown has also resulted in more than 50,000 deaths, and many in Mexico do not think the heightened violence has been too high a price to pay. On Thursday, 30,000 people dressed in white marched in silence through the city of Guadalajara in protests of the drug violence.
Recently, 11 local university students in Guadalajara have been murdered and 18 mutilated bodies were discovered dumped near the city limits earlier this month, which has residents demanded that the government solve the murders, or get out, student union leader Marco Antonio Nunez Becerra told the BBC.