The US government will stop collecting billions of domestic call records each year, should the legal authority expire later this year.
But a loophole in a secret court order would allow the government to carry on spying on US citizens regardless of whether or not it has legal grounds.
According to Reuters on Monday, a spokesperson for the Obama administration's National Security Council conceded that it may have to wind down the bulk phone records collection program, despite being a "critical national security tool."
"Allowing Section 215 [the law that allows the collection] to sunset would result in the loss, going forward, of a critical national security tool that is used in a variety of additional contexts that do not involve the collection of bulk data," spokesperson Ned Price told the news agency.
Section 215 of the Patriot Act, which authorizes the National Security Agency (NSA) to collect calling records from phone companies in bulk -- so-called "metadata" -- expires on June 1. The existence of the phone records program was revealed by whistleblower Edward Snowden, who leaked a secret court order compelling Verizon to hand over its entire cache of customer records on a rolling basis.
However, little stands in the way of the NSA continuing to use the phone records program to conduct domestic surveillance after June 1.
A similarly secretive court order, declassified and released by the Foreign Intelligence Surveillance Court earlier this month, suggests Congress does not need to extend the legal authority in order for the government to carry on using the program.
First reported by National Journal earlier this month, a passage buried on the final pages of the order may allow the court to rubber-stamp the continued use of the program.
"If Congress, conversely, has not enacted legislation amending [Section 215] or extending its sunset date... the government is directed to provide a legal memorandum... addressing the power of the Court to grant such authority beyond June 1, 2015," it reads.
The NSA did not respond to comment at the time of writing. (If we hear back, we will update the piece.)
Some of the more privacy-minded members of Congress are acutely aware of the risks of not acting on the Patriot Act's sunset provisions -- whether it expires or not.
Rep. Zoe Lofgren (D- CA, 19th), whose California district houses some of the technology powerhouses of the world, warned in an earlier phone conversation with ZDNet that lawmakers have to act regardless of the authority's upcoming expiration.
Lofgren explained that she and other lawmakers were "mindful" of the law, and warned its lapsing would "not solve the problem" of certain kinds of surveillance.
Her colleague Sen. Ron Wyden (D-OR), a key figure in the post-Snowden battle to reform the intelligence agencies, first disclosed in mid-2013 that the US government was using a loophole to conduct surveillance on Americans.
The so-called "backdoor search" loophole was later covered in more detail by The Guardian, citing a document leaked by whistleblower Edward Snowden, that allowed the NSA to search US citizens' emails and phone calls without a warrant.
"Whether [Section 215] expires or not, the Fourth Amendment rights of Americans are still at risk," Lofgren said.