The 2011 reversal of a 2008 restriction let the National Security Agency search deliberately for Americans' communications in its massive databases, the Post said, citing newly declassified documents and interviews with government officials.
The Foreign Intelligence Surveillance Court also extended the length of time the NSA may legally hold onto intercepted U.S. communications, increasing it to six years from five, a recently released 2011 opinion by court Chief Judge John D. Bates said.
An undated, unsigned cover letter outlining the documents' release was posted on the Office of the Director of National Intelligence website.
A redacted, unclassified version of Bates' opinion can be read here.
Many details in the Post story were reported Aug. 9 by British newspaper The Guardian from documents leaked by former NSA contractor Edward Snowden. The Post confirmed the information from the declassified documents.
What was not earlier reported, the Post said, was the 2008 ban imposed by the court, at the government's request, on the very kinds of searches the Obama administration in 2011 got the court to allow once again.
The court decision written by Bates permitted the NSA "to query the vast majority" of its databases using email addresses and phone numbers of Americans and legal residents without a warrant.
The queries must be "reasonably likely to yield foreign intelligence information," the opinion said. Query results would be subject to NSA privacy rules.
Alex Joel, the Office of the Director of National Intelligence's civil liberties protection officer, told the Post the renewed authority was needed in case the NSA learned of a rapidly developing terrorist plot and suspects a U.S. person may be involved.
Searching for communications to, from or about that person could help determine what involvement the person has and whether he or she was in touch with surveillance-targeted terrorists, Joel told the newspaper.
Officials would not say how many searches have been conducted.
Wyden told the Post in a statement the court-approved rule change "authorized the NSA to conduct warrantless searches of individual Americans' communications using an authority intended to target only foreigners.
"Our intelligence agencies need the authority to target the communications of foreigners, but for government agencies to deliberately read the emails or listen to the phone calls of individual Americans, the Constitution requires a warrant," his statement said.
Senior administration officials told the Post they disagreed.
"If we're validly targeting foreigners and we happen to collect communications of Americans, we don't have to close our eyes to that," Robert S. Litt, the Office of the Director of National Intelligence's general counsel, told the Post in an interview.
"I'm not aware of other situations where once we have lawfully collected information, we have to go back and get a warrant to look at the information we've already collected."