Peter Ojeda, the head of an Orange County wing of the Mexican Mafia, has been convicted of federal charges of racketeering and conspiracy to commit assault and murder.
According to authorities, Ojeda controlled Latino street gangs in the county for 30 years.
Prosecutors also charged Ojeda with plotting from behind bars to kill a rival.
Ojeda ordered local gangs to pay taxes for permission to sell drugs and commit other crimes.
His ex-girlfriend was also charged with acting as a messenger for Ojeda when he was arrested.