The U.S. Supreme Court on Wednesday ruled that almost $2 billion in frozen Iranian assets must be turned over to American families of people killed in the 1983 bombing of a U.S. Marine Corps barracks in Beirut and other attacks blamed on Iran.

The court's 6-2 ruling dealt a setback to Iran's central bank, finding that the U.S. Congress did not usurp the authority of American courts by passing a 2012 law stating that the frozen funds should go toward satisfying a $2.65 billion judgment won by the families against Iran in U.S. federal court in 2007.

Bank Markazi had challenged a 2014 ruling by the New York-based 2nd U.S. Circuit Court of Appeals that the assets, bonds held in a Citibank trust account in New York, should be handed over to the more than 1,000 American plaintiffs.