Gangs run riot in the world. they are like a mob of people constantly protesting, yes? they are a blemish or stain on the fabric of society and must be stopped or sent to jail, or, reformed.
I think subliminal messages in the media could brain wash them to see that gangs are bad news, yes? these messages could be to the point, with pictures of gang leaders on the front page each day and the charges with them - in 'ghetto papers,' of course.
Or, they could try to get them to move to the same area far from everyone else? this would be like apartheid, in a way, but upon being convicted of gang activity, they could all be moved to an area where there are only other gangsters. this will keep the wolves and sheep separated, of course.
Or, they could demand that every house without an income is moved to similar suburbs. they could get a ton of wooden houses - if they cannot afford homes nor have identity documents, they cannot work, so must be moved somewhere where crime is acceptable, of course - not that it is acceptable, just "steal from that guy with the gun!"