The federal Secure Communities act targets undocumented migrants. Under the program, the fingerprints of people charged with any infraction of the law, including traffic violations, are to be sent to the Department of Homeland Security.
Police can detain undocumented migrants and refer their cases to Immigration and Customs Enforcement (ICE). Federal officials say the program is meant to find serious criminals.
There is widespread opposition to the law from immigrant groups and several states. Some have resisted enforcing the law. Resistance is now over. Homeland Security says state consent is not required and has cancelled agreements with 40 states.
The law will be imposed everywhere by 2013. Massachusetts and New York have been told to implement the law immediately.
ICE is credited with trying to clear up confusion about the law. They issued instructions that would reduce the number of immigrants detained for minor infractions such as speeding or driving without a license.