From this:

The Obama administration is starting to shut down a program that deputized local police officers to act as immigration agents.

Immigration and Customs Enforcement officials have trained local officers around the country to act as their agencies' immigration officers. Working either in jails or in the field, the officers can check the immigration status of suspects and place immigration holds on them.

The program, known as 287(g), reached its peak under President George W. Bush, when 60 local agencies signed contracts with ICE to implement it. But that trend slowed significantly under President Obama— only eight agencies have signed up since he took office, and none has done so since August 2010.

Now, in their proposed budget for the upcoming year, Department of Homeland Security officials say they will not sign new contracts for 287(g) officers working in the field and will terminate the "least productive" of those agreements — saving an estimated $17 million. All the contracts between ICE and local police agencies run for three years, so that portion of the program could be finished by November when the last contract for field officers expires.

The most well-known participant in the 287g program is Sheriff Joe Arpaio of Maricopa County, Arizona. He was and is a target of Janet Napolitano of the Department of Homeland Security and the Obama administration in general.

The alternative program to 287g is Secure Communities, but that only includes the jail component, not the field component.