In a unanimous decision, Justice Clarence Thomas said that a money laundering case cannot be proven merely by showing that funds were concealed while being transported.

In a separate 5-4 decision, the court said that money laundering refers to profits of an illegal operation, not gross receipts. The court's interpretation is a narrow one opposed by law enforcement agencies.

Justice Antonin Scalia said the narrow definition will not unduly burden authorities, who must show only that a single instance of unlawful activity was profitable.

Providing the crucial tie-breaking vote, Justice John Paul Stevens refused to go as far as Scalia, saying Congress favored a broader interpretation of the law in cases involving the operation of organized crime syndicates.