The National Security Agency will no longer use a controversial surveillance tactic that lets the spy agency sift through electronic communications to find communications about its surveillance targets, according to an official who has been briefed on a pending ruling from the secretive Foreign Intelligence Surveillance Court (FISC).

The FISC ruling is expected to be publicized soon, and to indicate that the NSA has stopped using this surveillance tactic because it couldn’t fully comply with procedures designed to protect Americans’ constitutional rights.

The New York Times first reported that the NSA will stop engaging in this particular surveillance tactic, known as “about” colletion.

It’s a significant change in how the U.S. government surveils people, which will cheer civil liberties advocates and worry conservatives who argue muscular surveillance is necessary to stop terrorism.

The surveillance tactic at issue is known as “about” collection, and allowed under Section 702 of the FISA Amendments Act. Section 702 lets the NSA store and read internet communications pertaining to foreign targets that move through American companies. “About” collection is the process by which the NSA searches through those electronic communications it collects as they’re in traffic in transit across the Internet backbone. Civil liberties advocates believe “about” collection may result in the NSA reading emails between Americans without a warrant.

This process is now going to stop.

“The NSA has secretly spied on Americans’ internet communications for years, continuously searching through the contents of emails and web-browsing activities in bulk,” said Patrick Toomey, an ACLU attorney who works on surveillance issues. “This kind of warrant-free, suspicion-free surveillance is exactly what the Fourth Amendment prohibits. Putting an end to this spying is an important step, but it is only a start to the broader reforms of Section 702 that are badly needed to safeguard Americans' privacy.”

The official who spoke with The Daily Beast said the intelligence community will stop doing “about” collection because its analysts couldn’t fully comply with minimization procedures designed to keep them from violating Americans’ Fourth Amendment privacy rights.

NSA analysts conduct “about” collection when they spy on foreigners who they believe are outside the United States. Section 702 of the FISA Amendments Act lets the NSA read the emails and listen to the phone calls of people who aren’t U.S. citizens and aren’t in America.

When the NSA engages in “about” collection, it searches through internet communications (without a warrant, of course) for references to a person it is surveilling. And that means NSA analysts may sometimes look at emails sent by American citizens without first getting a warrant.

To try to protect Americans’ Constitutional rights, the highly secretive Foreign Intelligence Surveillance Court has required that NSA analysts take certain steps to minimize how much their spying––including “about” collection––impacts Americans’ rights. Those steps are called minimization procedures. Civil liberties advocates worry they don’t sufficiently protect Americans’ constitutional rights.

The NSA’s apparent struggles to comply with minimization procedures may be the reason the FISC it didn’t authorize any surveillance under Section 702, as indicated by a report on the court released last week.

The NSA’s decision to end “about” collection is also significant because the agency previously told the Privacy and Civil Liberties Oversight Board (PCLOB)––a bipartisan watchdog agency––that it would be difficult to stop “about” collection without stopping all “upstream surveillance.” The term “upstream surveillance” refers to the NSA’s practice of scanning communications in bulk as they pass over the Internet backbone, and saving copies of any that contained a term on the agency’s list of selectors.

This new ruling could mean one of two things: that either the NSA misinformed the PCLOB when it said it probably couldn’t stop doing “about” collection without stopping all “upstream surveillance,” or it found a way to do the former without doing the latter.

Regardless, this is a major change in how the U.S. government spies on foreigners it’s trying to surveil. And it’s the rare restriction in surveillance that has happened without Congressional involvement.

“There is a short list of things that civil liberties advocates honed in on as the biggest problems with 702,” said Julian Sanchez, who follows surveillance issues for the libertarian Cato Institute. “The other major one is the backdoor search loophole. But ‘about’ collection was probably the second on the list.”

“I think this is a useful narrowing of this very broad collections program,” he added, “something that’s at least a little bit closer to the traditional concept of surveillance, where the target is a person or account and not everything in the universe of communications that refers to that person or account.”