We the people ask the Department of Justice and the Department of Homeland Security, to classify "street gangs" as domestic terrorist groups. We ask that members and known associate's be dealt with in a similar way as we deal with foreign terrorist threats, such as Al Quada and Hezbollah.
Civil rights advocates will likely be appalled at the thought of this, but we can get around the fact that these people may or may not be US citizens. We will simply suspend Habeas Corpus for these individuals, much in the same way we executed Anwar al-Awlaki, another US citizen.
This will likely reduce inner city violence, as well as be a crime deterrent. With would be thugs knowing it will be illegal to pledge allegiance to any association other than the United States of America.