Abdus-Shahid M.S. Ali's lawsuit against prison guards was based on allegations of harassment and mistreatment. But the Supreme Court's decision yesterday that he is barred from suing rests on an ambiguous federal statute that has confounded the courts and sharply divided the justices.

It involves the word "any."

Ali's lawsuit alleging a missing Koran and prayer rug is barred under the Federal Tort Claims Act, the court said in a 5 to 4 ruling, because the law includes prison guards among those immune from suit.

The confusion in the courts comes because the immunity is mentioned in a section of the law that blocks lawsuits against the government over the "loss of goods, merchandise or other property" detained by customs or excise officers. The law then adds "or any other law enforcement officer."

"Congress could not have chosen a more all-encompassing phrase than 'any other law enforcement officer' " to show that it intended broad immunity, Justice Clarence Thomas wrote for the majority. Therefore, the law "forecloses lawsuits against the United States for the unlawful detention of property by 'any' not just 'some,' law enforcement officers."

Thomas was joined by Chief Justice John G. Roberts Jr. and Justices Antonin Scalia, Ruth Bader Ginsburg and Samuel A. Alito Jr.

Justice Anthony M. Kennedy wrote the dissent for the rest of the court. He said the court was wrong not to look at the context of the statute -- that it related to customs rather than prisons -- and said the implications of the decision were great.

"The seizure of property by an officer raises serious concerns for the liberty of our people and the Act should not be read to permit appropriation of property without a remedy in tort by language so obscure and indirect," Kennedy wrote.

Ali said in lower-court proceedings that the Koran, prayer rug and other religious materials -- worth about $177 -- went missing during his transfer from a federal penitentiary in Atlanta to Big Sandy prison in Kentucky. He alleged it was one of a number of incidents of mistreatment and harassment of Muslim prisoners.

But a district court said the lawsuit was barred by federal law, and the U.S. Court of Appeals for the 11th Circuit agreed. It is one of six circuits that have read the law to cover all law enforcement officers, in the same manner as Thomas and the court majority. Five circuits have read the law to limit the protection to officers performing customs or excise functions.

Justice Stephen G. Breyer agreed with Kennedy's dissent and added his own to reinforce his view of the importance of context.

"When I call out to my wife, 'There isn't any butter,' I do not mean, 'There isn't any butter in town,' " Breyer wrote. "The context makes clear to her that I am talking about the contents of our refrigerator.

"That is to say, it is context, not a dictionary, that sets the boundaries of time, place and circumstances within which words such as 'any' will apply," Breyer wrote.

The court's decision extends the law to "tens of thousands of officers performing unrelated tasks" to those covered by the statute, Breyer said.