The US supreme court will be asked to suspend the blanket collection of US telephone records by the FBI under an emergency petition due to be filed on Monday by civil rights campaigners at the Electronic Privacy Information Center (Epic).
This new legal challenge to the power of government agencies to spy on Americans follows the publication last month by the Guardian of a secret order from the Foreign Intelligence Surveillance Court ordering Verizon to hand over metadata from its phone records.
Previous attempts to appeal against the rulings of these courts have floundered due to a lack of public information about who might be caught up in the surveillance net, but the disclosure of specific orders by National Security Agency whistleblower Edward Snowden has opened the door to a flurry of new challenges. It comes as a similar legal challenge was filed in Britain on Monday.
The latest from Epic asks the supreme court to rule that the NSA and FBI have stretched the law governing state intrusion to such a point that checks and balances put in by lawmakers have become meaningless.
Under section 1861 of Foreign Intelligence Surveillance Act (Fisa), authorities seeking such records from phone companies must show "that there are reasonable grounds to to believe that the tangible things sought are relevant to an authorized investigation".
But lawyers acting for Epic argue that the sweeping nature of Fisa court orders revealed by Snowden make a mockery of this "relevancy" clause.
"It is simply not possible that every phone record in the possession of a telecommunications firm could be relevant to an authorized investigation," says a copy of the petition seen by the Guardian.
"Such an interpretation of Section 1861 would render meaningless the qualifying phrases contained in the provision and eviscerate the purpose of the Act."
The petition seeks a "writ of mandamus" to immediately overturn the order of the lower court, presided on in secret by judge Roger Vinson, or alternatively a "writ of certiorari" to allow supreme court justices to review the decision.
Epic lawyers also argue the original order is unconstitutional because it gives too much power to federal agencies, which could be abused to interfere in other areas of government.
"Because the NSA sweeps up judicial and congressional communications, it inappropriately arrogates exceptional power to the executive branch," says the petition.
A number of other legal challenges have been launched since Snowden's leaks began to be reported by the Guardian and Washington Post last month.
The American Civil Liberties Union filed a lawsuit with a Federal court in New York which accused the US government of a process that was "akin to snatching every American's address book".
It claimed the NSA's acquisition of phone records of millions of Verizon users violates the first and fourth amendments, which guarantee citizens' right to association, speech and to be free of unreasonable searches and seizures.
And on Capitol Hill, a group of US senators have introduced a bill aimed at forcing the US federal government to disclose the opinions of the FISA court that determines the scope of the eavesdropping on Americans' phone records and internet communications.
[Digital surveillance image via Shutterstock]