Over the past several years, the number of aliens who unlawfully reside in the United States has grown significantly, from an estimated 3.2 million in 1986 to more than 11 million in 2005. Although the federal government is responsible for regulating the entry and removal of aliens from the United States, the impact of unauthorized immigration has arguably been felt most directly in the communities where aliens settle. The response of states and localities to the influx of illegal immigrants has varied. On one end of the spectrum, some jurisdictions have actively sought to deter the presence of illegal immigrants within their territory. Some jurisdictions have assisted federal authorities in apprehending and detaining unauthorized aliens, including pursuant to agreements (287(g) agreements) with federal immigration authorities enabling respective state or local law enforcement agencies to carry out various immigration enforcement functions. More controversially, some jurisdictions have sought to deter illegal immigration by imposing their own restrictions upon unauthorized aliens' access to housing, employment, or municipal services. Moving toward the middle of the spectrum, some states and localities communicate with federal immigration enforcement officers under limited circumstances (e.g., after arresting an unauthorized alien for a criminal offense), but for various reasons do not take a more active role in deterring illegal immigration. At the other end of the spectrum, some jurisdictions have been unwilling to assist the federal government in enforcing measures that distinguish between legal and non-legal residents of the community. Some of these jurisdictions have adopted formal or informal policies limiting cooperation with federal immigration authorities. This latter category of jurisdictions is sometimes referred to as "sanctuary cities." Although this term is not defined by federal statute or regulation, it has been used by some in reference to "jurisdictions that may have state laws, local ordinances, or departmental policies limiting the role of local law enforcement agencies and officers in the enforcement of immigration laws." The very existence of "sanctuary cities" has been the subject of considerable controversy. Supporters argue that immigration enforcement is the responsibility of the federal government, and that local efforts to deter the presence of unauthorized aliens would undermine community relations, disrupt municipal services, interfere with local enforcement, or violate humanitarian principles. Opponents of sanctuary policies argue that they encourage illegal immigration and undermine federal enforcement efforts. The primary federal restrictions on state and local sanctuary policies are SS 434 of the Personal Responsibility and Work Opportunity Reconciliation Act of 1996 (PRWORA, P.L. 104 - 193 ) and SS 642 of the Illegal Immigration Reform and Immigrant Responsibility Act of 1996 (IIRIRA, P.L. 104 - 208 ). PRWORA SS 434 proscribes any prohibition or restriction placed on state or local governments to send or receive information regarding immigration status of an individual to or from federal immigration authorities. IIRIRA SS 642 is broader in scope. It bars any prohibition on a federal, state, or local governmental entity or official's ability to send or receive information regarding immigration or citizenship status to or from federal immigration authorities. The statute also provides that no person or agency may prohibit a federal, state, or local government entity from (1) sending information regarding immigration status to, or requesting information from, federal immigration authorities; (2) maintaining information regarding immigration status; or (3) exchanging such information with any other federal, state, or local government entity. The constitutionality of the foregoing provisions was challenged by the City of New York. The mayor of the City of New York had issued an Executive Order prohibiting any city officer or employee, in most circumstances, from transmitting information regarding immigration status to federal immigration authorities. This Executive Order was in direct conflict with both PRWORA SS 434 and IIRIRA SS 642. The United States Court of Appeals for the Second Circuit held in New York v. United States ( City of New York ) that PRWORA SS 434 and IIRIRA SS 642, on their face, do not violate the anti-commandeering doctrine under the Tenth Amendment. The anti-commandeering doctrine prohibits the federal government from commandeering either a state's legislature (e.g., by requiring that a state enact particular regulatory standards ) or its executive officers (e.g., by requiring that state officers directly participate in enforcing federal law ) to achieve federal goals. While this might mean that Congress cannot directly compel states to collect and share information regarding immigration status with federal immigration authorities, merely prohibiting states and localities from blocking their agents from sharing with the federal government information already in their possession may be permissible, according to the Second Circuit, absent specific proof of greater interference with state and local functions. Although several localities reportedly have adopted formal or informal policies limiting cooperation with federal immigration authorities, the precise number is unclear. In 2006, Congress required the Office of the Inspector General (OIG) for the Department of Justice to study and report on whether states and localities receiving federal compensation for incarcerating criminal aliens were cooperating with federal immigration enforcement efforts. Among other things, the OIG was required to determine whether any states or localities receiving compensation were in violation of the information-sharing requirements of IIRIRA SS 642. In a January 2007 report, the OIG stated that auditors were able to locate an official "sanctuary" policy for only two jurisdictions that received at least $1 million in SCAAP [State Criminal Alien Assistance Program] funding, the State of Oregon, which received $3.4 million, and the City and County of San Francisco, which received $1.1 million and has designated itself as a "City and County of Refuge." We also located an Executive Order issued by the Mayor of the City of New York limiting the activities of local law enforcement agencies and officers in the enforcement of immigration law. However, in each instance the local policy either did not preclude cooperation with ICE [Immigration and Customs Enforcement] or else included a statement to the effect that those agencies and officers will assist ICE or share information with ICE as required by federal law. The OIG report identified two jurisdictions receiving at least $1 million in SCAAP funding that had official sanctuary policies, but it concluded that neither violated federal law. The OIG estimate of jurisdictions with policies in direct violation of IIRIRA SS 642, however, is not comprehensive. While the OIG report indicated that few, if any, jurisdictions that received at least $1 million in SCAAP funding during FY2005 had formal policies violating IIRIRA SS 642, the report did not identify, for example, whether any jurisdictions receiving less the $1 million were in violation of federal law. Although IIRIRA SS 642 prohibits states and localities from barring the transfer or maintenance of information regarding immigration status, it does not require entities to collect such information in the first place. Reportedly, some states and localities seeking to limit assistance to federal immigration authorities have barred agencies or officers from inquiring about persons' immigration status, a practice sometimes described as a "don't ask, don't tell" approach. Though this method does not directly conflict with federal requirements that states and localities permit the free exchange of information regarding persons' immigration status, it results in specified agencies or officers lacking any information about persons' immigration status that they could share with federal authorities. In the 110 th Congress, several bills were introduced that attempted to limit formal or informal sanctuary policies and induce greater sharing of immigration information by state and local authorities. Some proposals would have mandated that directors of state and local law enforcement agencies report any immigration information collected in the course of the directors' normal duties to the Secretary of Homeland Security, and would have made compliance with this requirement a condition for continued funding under the State Criminal Alien Assistance Program (SCAAP). Other proposals would have required state and local law enforcement officers to provide information to the Secretary of Homeland Security concerning apprehended aliens who are believed to have committed a violation of U.S. immigration laws, and would have provided grants to those agencies that had policies for assisting in the enforcement of U.S. immigration laws. Some proposals would have made compliance with IIRIRA SS 642 a requisite for a state or locality to receive specified federal grants or funding. These proposals were not enacted into law. Bills have been introduced in the 111 th Congress to modify requirements on states and localities concerning the sharing of immigration-related information with the federal government. H.R. 150 , the Illegal Alien Crime Reporting Act of 2009, introduced by Representative Walter B. Jones, would bar any state or subdivision thereof from receiving funds under any program or activity administered by the Department of Homeland Security, unless the state reports to the Federal Bureau of Investigation certain immigration-related information regarding persons who have been arrested, charged with, or convicted of a crime by the state. S. 95 , introduced by Senator David Vitter, would prohibit any funds appropriated for the Community Oriented Policing Services Program from being used in contravention of IIRIRA SS 642. H.R. 264 , the Save America Comprehensive Immigration Act of 2009, introduced by Representative Sheila Jackson-Lee, would repeal IIRIRA SS 642 and PRWORA SS 434, thereby permitting states and localities to restrict the sharing of immigration-related information with federal authorities.

Summary:
Controversy has arisen over the existence of so-called "sanctuary cities." The term "sanctuary city" is not defined by federal law, but it is often used to refer to those localities which, as a result of a state or local act, ordinance, policy, or fiscal constraints, place limits on their assistance to federal immigration authorities seeking to apprehend and remove unauthorized aliens. Supporters of such policies argue that many cities have higher priorities, and that local efforts to deter the presence of unauthorized aliens would undermine community relations, disrupt municipal services, interfere with local law enforcement, or violate humanitarian principles. Opponents argue that sanctuary policies encourage illegal immigration and undermine federal enforcement efforts. Pursuant to SS 434 of the Personal Responsibility and Work Opportunity Reconciliation Act of 1996 (PRWORA, P.L. 104-193) and SS 642 of the Illegal Immigration Reform and Immigrant Responsibility Act of 1996 (IIRIRA, P.L. 104-208), states and localities may not limit their governmental entities or officers from maintaining records regarding a person's immigration status, or bar the exchange of such information with any federal, state, or local entity. Reportedly, some jurisdictions with sanctuary policies take a "don't ask, don't tell" approach, where officials are barred from inquiring about a person's immigration status in certain circumstances. Though this method does not directly conflict with federal requirements that states and localities permit the free exchange of information regarding persons' immigration status, it results in specified agencies or officers lacking information that they could potentially share with federal immigration authorities. In the 110th Congress, several bills were introduced that attempted to limit formal or informal sanctuary policies and induce greater sharing of immigration information by state and local authorities. Bills have also been introduced in the 111th Congress to restrict or expand states and localities' information-sharing requirements.