Use a firearm, face adult penalties and time.  Face deportation for any members of the household of a gang member.  Prohibit gang members and their families from living in apartments or rentals.  Prohibit their households from receiving section 8 or SNAP.  Start calling them by name, publish their pictures, and of what crime they did.    Allow the police to stop and search without probable cause. Make the USA a very unpleasant place to be.