WASHINGTON - The US Supreme Court on Thursday ruled in favor of an Arizona immigration law that penalizes companies that knowingly hire illegal immigrants.

The justices voted 5 to 3 to uphold the law, which was signed by then governor Janet Napolitano, now Secretary of Homeland Security in the Obama administration.

The law permits state authorities to revoke the business licenses of companies that knowingly hire illegal workers. It also requires employers to use an otherwise optional federal verification program to determine whether potential employees are eligible to work within the United States.

These measures were opposed by business groups and civil rights organizations, as well as the Obama administration.

"The state's licensing provisions fall squarely within the federal statute's savings clause and ... the Arizona regulation does not otherwise conflict with federal law," Chief Justice John Roberts wrote in the majority opinion.

All three dissents, Justices Stephen Breyer, Ruth Bader Ginsburg and Sonia Sotomayor, were appointed by Democratic presidents. Justice Elena Kagan did not participate because she worked on it while serving as Obama's solicitor general.