A federal judge will hear arguments Thursday over whether Arizona's new immigration should take effect on July 29.
It will mark the first major hearing in one of the seven challenges to the strict law.
U.S. District Judge Susan Bolton also will consider arguments over Gov. Jan Brewer's request to dismiss the challenge filed by Phoenix police Officer David Salgado and the statewide nonprofit group Chicanos Por La Causa.
The judge said last week that she wasn't making any promises on whether she will rule on the officer's request to block enforcement of the law before it takes effect.
The law requires police, while enforcing other laws, to question a person's immigration status if officers have a reasonable suspicion that the person is in the country illegally.