Revelations of America's industrial-scale surveillance have painted an alarming picture of the National Security Agency as a spy service operating virtually without limits since the 9/11 attacks, experts say.
Disclosures from intelligence leaker Edward Snowden have revealed how far the NSA has pushed the envelope in its digital snooping after being granted sweeping powers by Congress in the aftermath of the September 11, 2001 attacks.
The Patriot Act and other laws adopted after 9/11 "basically unleashed what we see today," said Gordon Adams, a professor at American University, who served as a senior official in Bill Clinton's administration.
"In a climate of fear, we basically took the reins off of accountability for the intelligence community."
Congress "opened up a floodgate" and both president George W Bush and Barack Obama justified the approach by citing the threat posed by Al-Qaeda, Adams told AFP.
"This is a bipartisan project," he added. "The reality is the law gave them (NSA) immense running room and they have seized every inch of that running room and then some."
The agency and its defenders say the NSA has always operated legally but some lawmakers and civil liberties groups charge the agency went beyond even the generous boundaries set by Congress, especially when it comes to gathering up "meta-data."
In the wake of Snowden's bombshell leaks, foreign governments from Brazil to France have voiced outrage about eavesdropping and lawmakers are now pushing for stricter limits on the NSA's spying authority, putting the White House on the defensive.
"We want to ensure we are collecting information because we need it and not just because we can," Lisa Monaco, assistant to the president for homeland security and counter-terrorism, wrote in a commentary Thursday in USA Today.
While the Obama administration was reviewing its surveillance policies, she said the US spy services have "more restrictions and oversight than in any other country in history."
Revulsion at spying abuses led to reforms in the 1970s empowering a surveillance court to review NSA eavesdropping and envisaged Congress as a watchdog to check excesses.
But rights advocates argue that Congress has failed to hold the NSA to account over the past decade, and that the spy agency also failed to give lawmakers a true picture about its vast digital dragnet of on line traffic and other espionage.
US intelligence officials "repeatedly misled Congress," said Greg Nojeim at the Center for Democracy & Technology.
