Kate Martin, director of the Center for National Security Studies, said, “If they don’t get a court order, it’s a crime.” Ms. Martin said that while the F.B.I. might be able to get access to phone collection databases by using an administrative subpoena, her reading of federal law was that the N.S.A. would be banned from doing so without court approval.

But another expert on the law of electronic surveillance, Kenneth C. Bass III, said that if access to the call database was granted in response to a national security letter issued by the government, “it would probably not be illegal, but it would be very troubling.”

“The concept of the N.S.A. having near-real-time access to information about every call made in the country is chilling,” said Mr. Bass, former counsel for intelligence policy at the Justice Department. He said the phone records program resembled Total Information Awareness, a Pentagon data-mining program shut down by Congress in 2003 after a public outcry. ~The New York Times