Mere membership in a gang should get 10 years minimum, regardless of their legal status. While in prison, gang members should have all tattoos forcibly removed, and to keep order, they should be castrated and lobotimized if they get out of line. If they kill anyone, they should be executed by public hanging. Any illegals that survive the hard time should be deported back to their country of origin after they have DNA taken from them, and implanted with an RFID chip that would immediately alert authorities if they re-enter the country.
Gang problem solved. Sorry, lefties: 'cruel and unusual punishment' refers only to human beings. Rabid animals like gang members need to be treated as such.