America's intelligence chief has released more documents that tell how the National Security Agency was given the go-ahead to start collecting bulk phone and internet records in the hunt for al Qaida terrorists.
They also shed light on how a court eventually gained oversight of the programme after the Justice Department obeyed a federal court order to release its previous legal arguments for keeping the programmes secret.
In a statement, director of national intelligence James Clapper explained that President George Bush first authorised the spying in October 2001 as part of the Terrorist Surveillance Programme, just after the September 11 attacks. Mr Bush disclosed the programme in 2005.
The Terrorist Surveillance Programme - which had to be extended every 30-60 days by presidential order - was eventually replaced by the Foreign Intelligence Surveillance Act - a law that requires a secret court to approve the bulk collection.
A senior intelligence official said the documents were released in connection with two long-running class-actions cases against the NSA in California. At the judge's direction, the administration reviewed previous declarations in order to relate information that was no longer classified and determined what could be released.
The disclosures are part of the White House's campaign to justify the NSA surveillance following leaks to the media about the secret programmes by former agency contractor Edward Snowden.
President Barack Obama hinted on Friday that he would consider some changes to NSA's bulk collection of Americans' phone records to address the public's concerns about privacy.
His comments came in a week where a federal judge declared NSA's collection programme "unconstitutional" and a presidential advisory panel suggested 46 changes to NSA operations. The recommendations included forcing the NSA to go to the court for every search of the phone records database and keeping that database in the hands of a third party - not the government.
The judge said there was little evidence any terror plot had been thwarted by the programme, known as Section 215 of the USA Patriot Act. The panel recommended continuing the programme but seeking a court order for each NSA records search. Mr Obama said he would announce his decisions in January.
"There has never been a comprehensive government release ... that wove the whole story together - the timeline of authorising the programmes and the gradual transition to (court) oversight," said Mark Rumold, staff lawyer at the Electronic Frontier Foundation, a civil liberties group suing the NSA to reveal more about the bulk records programmes.
"Everybody knew that happened, but this is the first time I've seen the government confirm those twin aspects."
That unexpected windfall of disclosures came along with the release of documents outlining why releasing the information would hurt national security. The US District Court in the Northern District of California had in the autumn ordered the Obama administration to make the documents, known as state secrets declarations, public .
The Justice Department issued the declarations late on Friday night in two continuing class action cases: Shubert v Bush, now known as Shubert v Obama, on behalf of Verizon customers; and Jewel v NSA, on behalf of AT&T customers.
"In September, the federal court in the Northern District of California ... ordered the government to go back through all the secret ex-parte declarations and declassify and release as much as they could, in light of the Snowden revelations and government confirmations," Mr Rumold said yesterday.
"So what was released late last night was in response to that court order."
In one such legal argument, former National Intelligence Director Dennis Blair told the court in 2009 that revealing information - including how information was collected, whether specific individuals were being spied upon and what the programmes had revealed about al Qaida - could damage the hunt for terrorists.
"To do so would obviously disclose to our adversaries that we know of their plans and how we may be obtaining information," Mr Blair said. Much of his 27-page response is redacted.