8 U.S.C. § 1373: Communication between government agencies and the Immigration and Naturalization Service

Notwithstanding any other provision of Federal, State, or local law, a Federal, State, or local government entity or official may not prohibit, or in any way restrict, any government entity or official from sending to, or receiving from, the Immigration and Naturalization Service information regarding the citizenship or immigration status, lawful or unlawful, of any individual. Sending such information to, or requesting or receiving such information from, the Immigration and Naturalization Service. Maintaining such information. Exchanging such information with any other Federal, State, or local government entity. The Immigration and Naturalization Service shall respond to an inquiry by a Federal, State, or local government agency, seeking to verify or ascertain the citizenship or immigration status of any individual within the jurisdiction of the agency for any purpose authorized by law, by providing the requested verification or status information.