Government Access to Phone Calling Activity and Related Records: Legal Authorities [Updated January 25, 2007] [open pdf - 138KB]
"Media disclosures regarding an alleged National Security Agency (NSA) program designed to collect and analyze information on telephone calling patterns within the United States have raised interest in the means by which the Government may collect such information. The factual information available in the public domain with respect to any such alleged program is limited and in some instances inconsistent, and the application, if at all, of any possibly relevant statutory provisions to any such program is likely to be a very fact specific inquiry. It is possible that any information provided to the NSA from the telephone service providers was provided in response to a request for information, not founded on a statutory basis. If this were the case, such a request would not necessarily be limited by the statutory structures discussed below, but in some instances, depending upon the facts involved, might expose the telephone companies to some civil remedies or criminal sanctions. In addition, a request, not founded upon a statutory scheme, would appear to lack a means of compelling production of the information requested. […]This report summarizes statutory authorities regarding access by the government, for either foreign intelligence or law enforcement purposes, to information related to telephone calling patterns or practices."
CRS Report for Congress, RL33424