State and Local 'Sanctuary' Policies Limiting Participation in Immigration Enforcement [March 28, 2014] [open pdf - 355KB]
"This report discusses legal issues related to state and local measures that limit law enforcement cooperation with federal immigration authorities. The report begins by providing a brief overview of the constitutional principles informing the relationship between federal immigration authorities and state and local jurisdictions, including the federal government's power to preempt state and local activities under the Supremacy Clause, and the Tenth Amendment's proscription against Congress directly 'commandeering' the states to administer a federally enacted regulatory scheme. The report then discusses various types of measures adopted or considered by states and localities to limit their participation in federal immigration enforcement efforts, including (1) limiting police investigations into the immigration status of persons with whom they come in contact; (2) declining to honor federal immigration authorities' requests that certain aliens be held until those authorities may assume custody; (3) shielding certain unlawfully present aliens from detection by federal immigration authorities; and (4) amending or applying state criminal laws so as to reduce or eliminate the immigration consequences that might result from an alien's criminal conviction."
CRS Report for Congress, R43457