In the United States and Canada, a sanctuary city is a city that limits its cooperation with the national government effort to enforce immigration law. Leaders of sanctuary cities want to reduce the fear of deportation and possible family break-up among people who are in the country illegally, so that such people will be more willing to report crimes, use health and social services, and enroll their children in school. Municipal policies include prohibiting police or city employees from questioning people about their immigration status and refusing requests by federal immigration authorities to detain people beyond their release date, if they were jailed for breaking local law. Such policies can be set expressly in law (de jure) or observed in practice (de facto), but the designation "sanctuary city" does not have a precise legal definition. The Center for Immigration Studies, which advocates restrictive immigration policies, estimates that about 300 U.S. jurisdictions, including cities, counties and states, have adopted sanctuary policies.
Opponents of sanctuary cities argue that cities should assist the federal government in enforcing immigration law. Supporters of sanctuary cities argue that enforcement of federal law is not the duty of localities. Legal opinions vary on whether immigration enforcement by local police is constitutional. Studies which investigated the relationship between sanctuary status and crime have found that sanctuary policies either have no effect on crime or that sanctuary cities have lower crime rates and stronger economies than comparable non-sanctuary cities.
In the United Kingdom and Ireland, sanctuary city refers to cities that are committed to welcoming refugees, asylum seekers and others who are seeking safety. Such cities are now found in 80 towns, cities and local areas in England, Wales, Scotland and Ireland. The emphasis is on building bridges of connection and understanding, which is done through awareness raising, befriending schemes and forming cultural connections in the arts, sport, health, education, faith groups and other sectors of society.Glasgow, Sheffield and Swansea are noted Cities of Sanctuary.