Phoenix, Arizona (CNN) -- Arizona Gov. Jan Brewer signed a bill Friday that requires police in her state to determine whether a person is in the United States legally, which critics say will foster racial profiling but supporters say will crack down on illegal immigration.

The bill requires immigrants to carry their alien registration documents at all times and requires police to question people if there is reason to suspect that they're in the United States illegally. It also targets those who hire illegal immigrant day laborers or knowingly transport them.

The Republican governor also issued an executive order that requires additional training for local officers on how to implement the law without engaging in racial profiling or discrimination.

"This training will include what does and does not constitute reasonable suspicion that a person is not legally present in the United States," Brewer said after signing the bill.

"Racial profiling is illegal. It is illegal in America, and it's certainly illegal in Arizona," Brewer said.

The rules, to be established in by the Arizona Peace Officers Standards and Training Board, are due back to her in May. The law goes into effect 90 days after the close of the legislative session, which has not been determined.

What will Arizona's immigration law do?

Previously, officers could check someone's immigration status only if that person was suspected in another crime.

Brewer's executive order was in response to critics who argue that the new law will lead to racial profiling, saying that most police officers don't have enough training to look past race while investigating a person's legal status.

"As committed as I am to protecting our state from crime associated with illegal immigration, I am equally committed to holding law enforcement accountable should this stature ever be misused to violate an individual's rights," Brewer said.

She added that the law would probably be challenged in courts and that there are those outside Arizona who have an interest in seeing the state fail with the new measure.