Sanctuary cities are areas across the United States that limit the cooperation of local law enforcement with federal immigration agents. Opponents of sanctuary cities argue that these areas ‘breed crime’ (they don’t), violate federal law (nope), and undermine respect for the law (a much more subjective question). The assumption seems to be that that local law enforcement must cooperate with federal immigration agents. Perhaps many would be surprised to learn that sanctuary cities are more in line with the traditional division of powers between states and the federal government.
Throughout most of the twentieth century, state and local police forces in the United States did not enforce immigration laws. It is widely established that the power to regulate immigration rests with Congress, not states. Until recently, the Department of Justice’s longstanding position was that state and local police forces lacked the authority to arrest irregular migrants for the sole purpose of initiating civil removal proceedings. In other words, police could only arrest irregular migrants for criminal conduct, not violations of immigration law.
Although the federal government through the 1980s and 90s fostered more formal and institutionalized relationships with state and local governments to identify deportable noncitizens, these efforts really ramped up in the early 2000s as part of the war on terror. According to the revised policy of the Department of Justice, police officers possess the ‘inherent authority’ to enforce all immigration laws. As a result, police powers relating to immigration enforcement, including surveillance powers, have greatly expanded to facilitate deportations. The change in policy also led the federal government to place increasing pressure on local law enforcement to cooperate in immigration enforcement. Although the federal government may encourage such cooperation, the anti-commandeering doctrine prevents the federal government from mandating that states enforce federal laws, such as immigration laws.
Shortly after the September 11th terrorist attacks, the Bush Administration directed immigration officials to enter hundreds of thousands of civil immigration records into the National Crime Information Centre (NCIC) of the Federal Bureau of Investigation. The categories for inclusion in the NCIC have continually increased and now include student visa violators. The federal government claimed that through the expanded NCIC, local police forces would be better able to apprehend terrorists. Yet most of the records added in the post September 11th era were of Latino immigrants wanted for civil immigration violation charges.
The Secure Communities program, inaugurated in 2008, aimed to identify every non-citizen in custody and prioritize the removal of violent offenders. The Secure Communities program relied heavily on automated biometric identification and information sharing among federal, state, and local agencies. Once a police officer took an arrestee’s fingerprints, the prints automatically went to the Department of Homeland Security for verification of the person’s immigration status. When many localities opted not to participate in Secure Communities, the Department of Homeland Security declared the program to be mandatory, despite the lack of clear statutory authority or regulations governing the program. In November 2014, the Department of Homeland Security abolished the program, but Donald Trump has stated that he will renew it.
Immigration and Customs Enforcement (ICE) relies on local cooperation, often by issuing detainers that ask local law enforcement agencies or jails to keep a person detained for up to 48 hours after his release date. During this time, ICE decides whether to take a person into federal custody for removal purposes. However in 2014 a federal appeals court ruled that local agencies are not legally required to abide by ICE requests issued through detainers.
In short, voluntary state and local cooperation with federal immigration efforts have increased over the past 15-20 years. But let’s not pretend that this is a natural or established way of handling immigration enforcement. Sanctuary policies are not the illegal aberrations that opponents make them out to be.
 Tom K. Wong, ‘The Efforts of Sanctuary Policies on Crime and the Economy’ (2017) Center for American Progress, available at: https://www.americanprogress.org/issues/immigration/reports/2017/01/26/297366/the-effects-of-sanctuary-policies-on-crime-and-the-economy/
 Under the anti-commandeering principle, the federal government cannot force states to enforce federal laws, like immigration laws. Printz v. United States, 521 U.S. 898 (1997); Brian Schoeneman, ‘The Conservative Case for Sanctuary Cities’ (7 February 2017), available at: https://bearingdrift.com/2017/02/07/conservative-case-sanctuary-cities/. Galarza v. Szalczyk, et al (3d Circuit, March 4, 2014) establishes that ICE cannot require local law enforcement to carry out immigration detainers; Although 8 U.S.C. 1373 prohibits local governments from restricting communication with federal immigration authorities around a person’s citizenship or immigration status, many sanctuary cities “do not directly prohibit employees from providing information to federal immigration authorities.” Renee Sloan Holtzman Sakai LLP, ‘Can the President Defund Sanctuary Cities’, available at: http://publiclawgroup.com/2017/01/27/can-the-president-defund-sanctuary-cities/. See also, Andrew P. Napolitano, ‘Judge Andree Napolitano: Are Sanctuary cities legal?’, Fox News (8 December 2016), available at: http://www.foxnews.com/opinion/2016/12/08/judge-andrew-napolitano-are-sanctuary-cities-legal.html.
 Anil Kalhan, ‘Immigration Policing and Federalism Through the Lens of Technology, Surveillance, and Privacy’ (2013) 74 Ohio State L J 1105, 1111-1115.
 Kalhan (n. 3) 1111-1115.
 Kalhan (n. 3) 1111-1115.
 Michael Winshie, ‘State and Local Police Enforcement of Immigration Laws’ (2004) J of Constitutional L 1084, 1085-1095; James Walsh, ‘Watchful Citizens: Immigration Control, Surveillance and Societal Participation’ (2014) 23 Social & Legal Studies 237, 240.
 David A. Harris, ‘The War on Terror, Local Police, and Immigration Enforcement: A Curious Tale of Police Power in Post-9/11 America’ (2006) 38 Rutgers L J 1, 25-26.
 Doris Marie Provine and Gabriella Sanchez, ‘Suspecting Immigrants: Exploring Links Between Racialised Anxieties and Expanded Police Powers in Arizona’ (2011) 21 Policing & Society 468, 468; See William Bloss, ‘Escalating U.S. Police Surveillance After 9/11: An Examination of Causes and Effects’ (2007) 4 Surveillance & Society 208, 209.
 Harris (n. 7) 25-26.
 Kalhan (n. 3) 1122.
 Winshie (n. 6) 1087.
 Kalhan (n. 3) 1125.
 Harris (n. 7) 29.
 Kalhan (n. 3) 1126.
 Kalhan (n. 3) 1126.
 Elina Treyger, Aaron Chalfin, and Charles Loeffler, ‘Immigration Enforcement, Policing, and Crime: Evidence from the Secure Communities Program’ (2014) 13 Criminology & Public Policy 285, 286.
 Kalhan, 1129-1130.
 ACLU, ‘Immigration Detainers, available at: https://www.aclu.org/issues/immigrants-rights/ice-and-border-patrol-abuses/immigration-detainers
 Galarza v. Szalczyk, et al (3d Circuit, March 4, 2014); full opinion available here: https://www.immigrantjustice.org/litigation/blog/galarza-v-szalczyk-et-al