WASHINGTON – An appeals court Monday reinstated a lawsuit challenging a law giving the US government broad authority in electronic wiretapping and monitoring of overseas calls and emails in probing suspected terrorism.

The US Court of Appeals in New York said the suit by civil liberties activists can proceed, reversing a lower court decision dismissing the case.

The suit, filed by a coalition of groups including Amnesty International and Human Rights Watch, had been dismissed by a judge who said they had not established legal standing by showing their own communications had been monitored.

But the three-judge appeals panel said the plaintiffs "have established that they reasonably fear being monitored under the allegedly unconstitutional (law), and that they have undertaken costly measures to avoid it."

As a result, the plaintiffs "have established that they suffered present injuries in fact... stemming from a reasonable fear of future harmful government conduct."

The appeals court sent the measure back to a lower court to review the merits of the case.

The American Civil Liberties Union, one of the plaintiffs, hailed the action, saying that "Americans shouldn't have to accept as a fact of life that the government may be monitoring their international emails and phone calls and they can do nothing about it."

The plaintiffs also include media organizations and attorney David Nevin, who represents the accused 9/11 mastermind Khalid Sheikh Mohammed.

The case stems from a law approved by Congress in 2008 expanding legal authority for electronic wiretaps by spy agencies, giving then-president George W. Bush a victory in his anti-terror strategy.

The measure includes retroactive immunity for telecommunications firms which aided warrantless government surveillance operations following the September 11 attacks in 2001 -- a key demand of the White House.

The bill sparked fierce debate between civil liberties advocates who argue it eroded checks on the power of government and intelligence officials who feared the row was compromising their power to thwart terror attacks.

After the September 11, 2001 attacks, Bush authorized the National Security Agency to eavesdrop on calls and emails between the United States and abroad in cases that federal agents deemed may have a terror link.

The wiretaps went ahead without the permission of a special court set up to watch over government wiretapping operations inside the United States, provided for under the Foreign Intelligence Surveillance Act (FISA) of 1978.

The program, revealed in 2005, caused public outcry and opponents argued that US privacy guarantees meant the intelligence agencies should seek court warrants from the FISA court to conduct such spying inside the country.