Justices accepted an appeal from the state of Washington that involves fees paid to the Washington Education Association by teachers who decline to join the union.
Those workers still can be charged fees by the union to help pay for labor negotiations that affect them. But they can't be forced to pay for the union's political activism.
At issue is whether the union needs teachers to say "yes" before the fees can be used for political causes or whether the fees can be used for that purpose unless the teachers say "no."
The Washington Supreme Court overturned a 1992 law that required unions to get the consent of each worker and refund money to everyone who did not agree.
The court said the union's annual offer to reduce the fees for any nonmember who registers an objection to the use of fees for political purposes is sufficient.
The state court said that forcing the union to seek permission from each worker violated the union's free speech rights.
The three dissenters in the case, however, said the ruling "turned the First Amendment on its head," by valuing the rights of the union above those of individuals.
Washington Attorney General Rob McKenna said the decision conflicted with prior court cases upholding similar laws.
The union is the state's largest teachers union. Fewer than 5 percent of the 80,000 people the union represents choose not to be members, the union said.
Arguing against the appeal, the Washington union said the state law is the only one in the nation that restricts otherwise lawful union spending.
The case stemmed from a complaint filed by the Evergreen Freedom Foundation, a conservative think tank based in Olympia, Wash. The foundation has fought for years with the union over the collection of fees from workers who choose not to join.
In other action Tuesday, the Supreme Court:
The Fair Credit Reporting Act requires companies to notify consumers about rate increases based on information in consumer credit reports.
Justices said they would review a decision by the 9th U.S. Circuit Court of Appeals, which said a lower court should consider Jeffrey Landrigan's claims that his lawyer was ineffective.
Landrigan escaped from an Oklahoma prison in 1989, where he was serving a 20-year term for murdering an acquaintance. A month later, he killed Chester Dyer, who picked up men on the Phoenix streets by flashing large sums of money.
In urging the Supreme Court to take the case of Luis Alexander Duenas-Alvarez, the Bush administration is challenging an appeals court ruling it says could have "a substantial effect on the administration of immigration laws."
The issue revolves around whether Duenas-Alvarez's conviction under California law qualifies for deportation under federal immigration law.