By a 5-3 vote, the court said Thursday that federal immigration law gives states the authority to impose sanctions on employers who hire unauthorized workers.
The decision upholding the validity of the 2007 law comes as the state is appealing a ruling that blocked key components of a second, more controversial Arizona immigration enforcement law. Thursday's decision applies only to business licenses and does not signal how the high court might rule if the other law comes before it.
Chief Justice John Roberts, writing for a majority made up of Republican-appointed justices, said the Arizona's employer sanctions law "falls well within the confines of the authority Congress chose to leave to the states."
Justices Stephen Breyer, Ruth Bader Ginsburg and Sonia Sotomayor, all Democratic appointees, dissented. The fourth Democratic appointee, Justice Elena Kagan, did not participate in the case because she worked on it while serving as President Barack Obama's solicitor general
Breyer said the Arizona law upsets a balance in federal law between dissuading employers from hiring illegal workers and ensuring that people are not discriminated against because they may speak with an accent or look like they might be immigrants.
Employers "will hesitate to hire those they fear will turn out to lack the right to work in the United States," he said.
.Business interests and civil liberties groups challenged the law, backed by the Obama administration.
The measure was signed into law in 2007 by Democrat Janet Napolitano, then the governor of Arizona and now the administration's Homeland Security secretary.
The employer sanctions law has been only infrequently used. It was intended to diminish Arizona's role as the nation's hub for immigrant smuggling by requiring employers to verify the eligibility of new workers through a federal database. Employers found to have violated the law can have their business licenses suspended or revoked.
Lower courts, including the San Francisco-based 9th U.S. Circuit Court of Appeals, previously upheld the law.
The case is Chamber of Commerce v. Whiting, 09-115.