A US appeals panel has upheld the supposed constitutionality of a controversial federal law that grants immunity to telecommunications companies assisting in the surveillance of American citizens.

The latest ruling effectively reinforces the 2008 decision of Congress to grant telecoms immunity for cooperating with the government’s intelligence-gathering activities.

According to Judge Margaret McKeown of the 9th Circuit, the above-mentioned immunity does not "close" the courts for those wishing to challenge such actions, as only the telecommunications companies are covered by the ruling - rather than the government itself.

"The federal courts remain a [valid] forum to consider the constitutionality of the wiretapping scheme and other claims," she wrote in a ruling obtained by Reuters. 

Unsurprisingly, the Electronic Frontier Foundation (EFF) issued an official statement decrying the decision.

"By passing the retroactive immunity for the telecoms' complicity in the warrantless wiretapping program, Congress abdicated its duty to the American people," said EFF Senior Staff Attorney Kurt Opsahl.

"It is disappointing that today's decision endorsed the rights of telecommunications companies over those over their customers."