The U.S. Supreme Court has heard oral arguments in an important immigration case from the southwestern state of Arizona. At issue is whether Arizona has the right to punish employers who knowingly hire illegal aliens and whether that conflicts with the federal government's responsibility to enforce immigration laws. 

Under a state law approved in Arizona in 2007, the state has the right to sanction employers who knowingly hire illegal immigrants.

But an unusual mix of civil rights and business groups is challenging the state law in court, and the case was presented for oral argument before the Supreme Court.

Critics of the Arizona statute say the state law conflicts with the federal government's traditional role in enforcing immigration laws.

Carter Phillips argued the case against the Arizona law on behalf of a diverse coalition of critics that includes the U.S. Chamber of Commerce, the American Civil Liberties Union, and the Mexican American Legal Defense Fund.