There’s no official legal definition for sanctuary city and what it means varies significantly from place to place. Generally speaking, local law enforcement in sanctuary cities or counties don’t ask or report the immigration status of people they come into contact with.A sanctuary jurisdiction typically refuses requests from federal immigration authorities to detain undocumented immigrants apprehended for low-level offenses. A sanctuary city would also refuse to have its local law enforcement "deputized" as federal immigration agents.
City of Columbus, Ohio:
Other Sources of Law on Sanctuary Cities