Fight Gangs by Enforcing Immigration
Behind the disputes in Illinois is a federal program called Secure Communities, under which local police and jail authorities share fingerprints with federal immigration agents of everyone they book. The Obama administration has rapidly expanded the program across the country, with Illinois being one of only two states — the other is Alabama — where it has not been put into effect.
http://www.thedailybeast.com/articles/2012/07/11/chicago-immigration.html