Arizona Governor Jan Brewer signed a tough new immigration bill into law on Friday.
The law would require police officers to ask anyone suspected of being in the country illegally about their immigration status. It would also give them broad powers to detain anyone unable to produce proof of their citizenship status.
Opponents of the measure say it will lead to discrimination towards Hispanics.
Speaking at the White House earlier in the day, President Barack Obama criticized the measure. He ordered the Justice Department to look to see if the measure would violate civil rights. Obama says the Arizona law should prod lawmakers to enact immigration reform and failing to do so will lead to what he calls more "misguided" efforts like the Arizona bill.
Governor Brewer says the new law "protects every Arizona citizen." She also says the law fixes a problem that "the federal government has refused to fix."
The law will take effect in 90 days.