Critics of the Arizona law predict it will lead to discrimination against Latinos if police are authorized to question motorists and pedestrians about their immigration status. It will "cause intolerable harassment and lengthy detentions," Lucas Guttentag, who teaches immigration law at Yale University and Stanford University, said after the oral arguments.
If the high court were to revive the stop-and-arrest provisions, Arizona could move to enforce the law.
But it would not end the legal battle. Civil rights and civil liberties groups are challenging the measure on different grounds from the Obama administration, saying it would lead to racial profiling and harassment of Latino residents and violate their civil rights.
Last year, the U.S. 9th Circuit Court of Appeals put on hold four parts of the Arizona law, which was passed in 2010. Elsewhere, judges have blocked parts of similar laws in Alabama, Georgia, South Carolina, Indiana and Utah, awaiting a ruling from the high court.
Only eight justices will rule on the case, probably in late June. Justice Elena Kagan, who preceded Verrilli as the Obama administration's solicitor general, stepped aside, probably because she worked on the case before joining the Supreme Court. A 4-4 tie would preserve the 9th Circuit's ruling.