Under this standard, it's not unusual for agencies to use civil investigative demands or other administrative subpoenas to obtain ongoing access to large data sets when necessary to preserve the data and to search for records germane to the investigation. That occurs in all manner of regulatory and law enforcement investigations.
One salient example is the administrative subpoenas issued by the Treasury Department to acquire a database of transactional records relating to interbank financial transfers. This allows Treasury investigators to conduct focused queries for evidence of terrorist-related transactions.
If the NSA is singled out and prohibited from relying on this common relevance standard to assemble the telephone metadata collection under FISA, Americans will be distinctly less safe.
Some have argued that the data should remain under the control of the phone companies and that the NSA should have only secondhand access.
That may be an appropriate alternative for the Securities and Exchange Commission or other regulatory agencies that often rely on private companies or third-party vendors to maintain databases needed for investigations.
But such a change would render the NSA's metadata program less effective, less secure and less responsive to executive branch and congressional oversight. Those are not desirable goals.
Many libertarians are quick to condemn the NSA's collection of telephone metadata as an example of government overreach and encroachment into Americans' private freedom.
But protecting the United States from foreign attack is the core mission of the federal government, and a catastrophic failure in that mission could threaten the liberties we all cherish.
Moreover, it's profoundly unfair to tar the NSA as irresponsible or an agency run amok. In my experience, there is no more self-restrained, professional and patriotic group of federal officers than those staffing the NSA today.
We should be proud of the job this agency is doing and of the effectiveness and prudent focus of its metadata program.
Steven G. Bradbury was head of the Justice Department's Office of Legal Counsel from 2005 to 2009. In 2006, he led the department's legal effort to obtain initial approval from the Foreign Intelligence Surveillance Act court for the telephone metadata order.