"Yes, the F.B.I. could have stopped 9/11. It had a warrant to establish surveillance of everyone connected to Al Qaeda in America. It could follow them, tap their phones, clone their computers, read their e-mails, and subpoena their medical, bank, and credit-card records. It had the right to demand records from telephone companies of any calls they had made. There was no need for a metadata-collection program. What was needed was coöperation with other federal agencies, but for reasons both petty and obscure those agencies chose to hide vital clues from the investigators most likely to avert the attacks."
Edward Snowden has started a critical debate about the legality and the effectiveness of the N.S.A.'s practice of collecting unlimited records of telephone calls made to, from, and within the United States. Last month, two federal judges came to opposing conclusions about these issues. On December 16th, Judge Richard J. Leon, in Washington, D.C., ruled that the indiscriminate hoarding violates the Fourth Amendment right to privacy and its prohibition of unreasonable searches. Two weeks later, in New York, Judge William H. Pauley III ruled that the metadata-collection program was lawful and effective.
Judge Pauley invoked the example of Khalid al-Mihdhar, a Saudi jihadist who worked for Al Qaeda. On 9/11, he was one of the five hijackers of American Airlines Flight 77, which crashed into the Pentagon. In early 2000, Mihdhar made seven calls from San Diego to an Al Qaeda safe house in Yemen. According to Pauley, the N.S.A. intercepted the calls, but couldn't identify where Mihdhar was calling from. Relying on testimony by Robert Mueller, the former director of the F.B.I., Pauley concluded that metadata collection could have allowed the bureau to discover that the calls were being made from the U.S., in which case the bureau could have stopped 9/11.