The US Supreme Court heard arguments Wednesday in an Arizona law designed to combat illegal immigration that prompted a national debate about immigration policy, DPA reported.
Officials in the south-western state of Arizona argued the law was necessary to combat an influx of undocumented immigrants from Mexico because US authorities had not done enough to enforce existing national laws.
But President Barack Obama's administration says the law preempts the federal government's authority to set immigration policy.
The controversial measure mandates state police to ascertain the immigration status of every suspect they detain, and allows local police to arrest those whom they suspect are in the country illegally.
The proposals were blocked by the courts in 2010 just a day before they were set to come into force. The 9th District Court of Appeals last year upheld the ruling on the grounds that the federal government has sole authority over immigration.