To the supporters of Arizona's law, the questioning requirement was the most important part of the statute, whose stated purpose was to reduce the problems associated with illegal immigration through enforcement by the state.
Immigrant rights groups believe the requirement presents the most opportunities for civil rights abuses.
Shortly before the law was to take effect in July 2010, Bolton prevented police from enforcing the questioning requirement and other parts of the statute, ruling the Obama administration would likely succeed in showing federal law trumps the state law.
Brewer appealed the ruling, lost at the 9th U.S. Circuit Court of Appeals and took her case to the Supreme Court.
Less controversial sections of the law have been in effect since late July 2010 but have rarely been used.
Arizona's law was passed amid voter frustration with the state's role as the busiest illegal entry point into the country. Five states — Alabama, Georgia, Indiana, South Carolina and Utah — have adopted variations of Arizona's law.
Brewer's office said the law is expected to go into effect shortly.
"The courts have now consistently found that the plaintiffs have not met the high bar in arguing this law needs to be enjoined before it's allowed to take effect," gubernatorial spokesman Matthew Benson said. "Certainly, Gov. Brewer is pleased with this decision. She believes it's time SB1070 is implemented and so that we can see how effective this law is in practice."
Karen Tumlin, an attorney for the National Immigration Law Center, said her office was "considering our legal options" after Bolton's ruling.
"We were surprised and disappointed," said Dan Pochoda, legal director for the American Civil Liberties Union of Arizona.
Bolton did, however, grant a preliminary injunction against a statute making it illegal to harbor individuals suspected of being in the country illegally.
Guzman, the Arizona civil rights activist, said she expects police to tread cautiously as they implement the requirement.
"They know they're under the watchful eyes of activists like me, attorneys and even their own departments," she said.
Riccardi reported from Denver. Associated Press writers Walter Berry in Phoenix and Felicia Fonseca in Flagstaff contributed to this report.
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