This latter category of jurisdictions is sometimes referred to as "sanctuary cities." 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. Applicable Law

The primary federal restrictions on state and local sanctuary policies are § 434 of the Personal Responsibility and Work Opportunity Reconciliation Act of 1996 (PRWORA, P.L. 104 - 193 ) and § 642 of the Illegal Immigration Reform and Immigrant Responsibility Act of 1996 (IIRIRA, P.L. 104 - 208 ). 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. 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. Legislative Activities

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. 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.
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 § 434 of the Personal Responsibility and Work Opportunity Reconciliation Act of 1996 (PRWORA, P.L. 104-193) and § 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.