The Obama administration intends to use part of a law banning the bulk collection of US phone records to temporarily restart the bulk collection of US phone records.

US officials confirmed to the Guardian that in the coming days they will ask a secret surveillance court to revive the program – deemed illegal by a federal appeals court – all in the name of “transitioning” the domestic surveillance effort to the telephone companies that generate the so-called “call detail records” the government seeks to access.

The unconventional and unexpected legal circumstance depends on a section of the USA Freedom Act, which Obama signed into law on Tuesday, that provides a six-month grace period to prepare the surveillance and legal bureaucracies for a world in which the National Security Agency is no longer the repository of bulk US phone metadata.

During that time, the act’s ban on bulk collection will not yet take effect.

But the NSA stopped its 14-year-old collection of US phone records at 8pm ET on Sunday, when provisions of the Patriot Act that authorized it until that point lapsed. The government will argue it needs to restart the program in order to end it.

US officials did not say if the secret Fisa court will hear arguments from the newly established “amicus”, who will be empowered by the Freedom Act to contest the government’s contentions before the previously non-adversarial court. The Freedom Act permits the amicus to argue before the court in novel circumstances.

“We are taking the appropriate steps to obtain a court order reauthorizing the program. If such an order is granted, we’ll make an appropriate announcement at that time as we have with respect to past renewal applications,” Marc Raimondi, the Justice Department’s national security spokesman, told the Guardian on Wednesday.

One of the leading congressional advocates for surveillance reform, Senator Ron Wyden, warned the Obama administration not to restart a program now roundly rejected by Congress and repudiated by a federal appeals court as illegal.

“I see no reason for the executive branch to restart bulk collection, even for a few months, and I urge them not to attempt to do so. This illegal dragnet surveillance violated Americans’ rights for 14 years without making our country any safer, and the administration should leave it on the ash heap of history,” Wyden, an Oregon Democrat and member of the Senate intelligence committee, told the Guardian on Wednesday.

Citing the “substantial legal uncertainty looming over bulk collection”, Wyden aide Keith Chu added that the senator “would expect an amicus to be appointed on this”.

Privacy-minded lawyers and campaigners said they had long expected the Obama administration would use the Freedom Act’s transition period to wind the bulk collection down. But they said that the grace period in the law did not envision the circumstance that Senate deadlock ended up creating – in which a dead surveillance program would need to be revived, rather than an ongoing one getting phased out.

“McConnell’s gamble on a clean reauthorization of [parts of the Patriot Act] without reform and his further attempts to weaken the privacy protections contained in the USA Freedom Act has caused this ridiculous situation in which the bulk metadata program is being reanimated in order to be shut down for good,” said Amie Stepanovich, an attorney with the digital-rights group Access.

It is unclear why the NSA believes it needs, as a technical matter, to restart the bulk collection that it has already ended. Under the Freedom Act, the FBI or NSA will obtain a court order from the Fisa court for call detail records once it has a “reasonable articulable suspicion” that a baseline number, account or device is connected to terrorism. From there, the telephone companies would turn over records of those communications, as well as records of communications made by the target’s contacts, for a six-month period.

Representatives for the NSA and the director of national intelligence did not respond to requests for an explanation.

Through a spokesperson, the current presiding judge on the Fisa court, Thomas Hogan, declined to comment.

The USA Freedom Act explicitly states that its bans on mass surveillance “shall take effect on the date that is 180 days after the date of the enactment of this Act”. During that period, however, the second circuit court of appeals’ ruling from 7 May that bulk phone data collection is illegal would seem to be in effect.

The ACLU, the plaintiff in the case the second circuit decided, is considering the implications of the new legislation for a follow-on action. One possibility, if the government succeeds in resurrecting bulk collection, is to ask the court to block the surveillance through an injunction.

“The administration is not bound by the second circuit outside that court’s jurisdiction, and in any event, the court imposed no remedy, instead sending it back to the lower court. But if they do restart the program, they will have some explaining to do in court,” said David Cole, a law professor at Georgetown University.

Stepanovich added: “While the USA Freedom Act allows for a period of six months to transition the collection of data outside of the NSA, the administration should actively work to move the program as quickly as possible. If the NSA takes the entire six months to stop indiscriminately collecting our data it is in violation of the spirit of the transition and needlessly continues to harm the privacy of users en masse. We need to move to the targeted collection codified by the USA Freedom Act without any delay.”

At the very least, lawyers said, the legality of restarting the bulk collection is both a novel and a disputable proposition, precisely the sort of circumstance Congress created the amicus to help resolve.

“Whether the NSA can restart this bulk collection is a novel question, and this decision should not be made in secret. The Fisa court should appoint an amicus – that’s what this provision of USA Freedom is for. And the decision and its reasoning should be made public,” said Jennifer Granick, director of civil liberties at the Stanford University Law School’s Center on Internet and Society.