"Congress has long supported efforts to identify, detain, and remove criminal aliens, defined as noncitizens who have been convicted of crimes in the United States. The apprehension and expeditious removal of criminal aliens has been a statutory priority since 1986, and the Department of Homeland Security (DHS) and one of its predecessor agencies have operated programs targeting criminal aliens since 1988. Investments in DHS's Immigration and Customs Enforcement (ICE) interior enforcement programs since 2004 have increased the number of potentially removable aliens identified within the United States. [...] PEP [Priority Enforcement Program], its predecessor Secure Communities, and the §287(g) program have all contributed to DHS removing large numbers of aliens in the past decade. Yet, these programs also have been controversial. Because interoperability screens all people passing through law enforcement jurisdictions, critics often charged ICE with removing many people who either committed minor crimes or who had no criminal record apart from unauthorized presence in the United States. Other critics charge that revisions to the set of enforcement priorities through PEP have since contributed to declining numbers of enforcement actions. The §287(g) program has raised concerns over inconsistent policies and practices among jurisdictions and allegations of racial profiling, among other issues. Such concerns caused ICE to revise the program in FY2012 and allow certain §287(g) agreements with law enforcement agencies to expire. Since then, immigration enforcement advocates have questioned why ICE has curtailed the program's use. ICE has recently expressed interest in expanding it. For these and other reasons, Congress may be interested in measures of enforcement levels by program, the level of appropriations for different criminal alien programs, and the role of state and local law enforcement agencies in immigration enforcement."
CRS Report for Congress, R44627