In 2013, former National Security Agency contractor Edward Snowden famously brought to light a series of classified US government spying programs. For the first time, the American people learned that the NSA was collecting millions of their phone calls and electronic communications—emails, Facebook messages, texts, browsing histories—all without a warrant.

Several of the programs Snowden revealed are authorized under Section 702 of the Foreign Intelligence Surveillance Amendments Act. The 2008 law was scheduled to sunset on December 31, but in a last-ditch effort Thursday, Congress extend its authority through January 19.

The Trump administration, meanwhile, believes that the authorization doesn’t really expire until April, leaving lawmakers several months to either reform or strengthen the provision. Hanging in the balance is the legal framework the government largely relies on to conduct mass surveillance of foreigners, and Americans who communicate with them. Which makes it all the more concerning that the fight over Section 702's future has taken place largely in the dark.

Swept Up

Section 702 is intended to allow intelligence officials to electronically surveil “persons reasonably believed to be located outside the United States” without a warrant. The provision was crafted after the Bush administration’s secret warrantless surveillance program, dubbed Stellar Wind, was disclosed to The New York Times by whistleblower and former Department of Justice prosecutor Thomas Tamm in 2005.

'We’re having a debate where the intelligence agencies are refusing to provide any information to Congress about the effectiveness of this program.' Neema Singh Guliani, ACLU

The NSA collects hundreds of millions of video chats, instant messages, and emails under Section 702 by compelling companies like Facebook, AT&T, and Google to hand them over. The law also allows the FBI to search through the NSA’s databases without a warrant. Section 702 technically only authorizes intelligence agencies to collect information about foreign individuals, but citizens and permanent residents can easily get swept up by dragnet.

“Under the authority, the government can target anybody who has ‘foreign intelligence,’ that’s defined so broadly,” says Neema Singh Guliani, legislative council at the ACLU. “If you’re a reporter who reports on global affairs, or an activist who works on global affairs, you could be a target under 702. We don’t have exact clarity on who's been targeted.”

Which only begins to get at the difficulty any discussion about Section 702 runs into. Democrats, Libertarians, and privacy groups believe it violates the Fourth Amendment, while Republicans argue that limiting its powers would impede national security. But most proponents of the expiring law, along with its detractors, don't truly know how Section 702 works. No one, except those with the right security clearances, really understands how the law is used, how many Americans it affects, or how effective the programs it authorizes are at catching terrorists. The only individuals with a detailed understanding of Section 702's programs are those inside the US intelligence apparatus.

“We’re having a debate where the intelligence agencies are refusing to provide any information to Congress about the effectiveness of this program and the effect it has on people’s liberties,” says Guliani. “You have a case where you have this massive program, and in many respects Congress is being asked to vote on it blind.”

Blurry Snapshots

While the intelligence community does provide statistics about how many foreigners Section 702 programs target, intelligence officials have refused to provide civil liberties groups and lawmakers with statistics about how many Americans’ communications are vacuumed up into its massive surveillance apparatus.

“There are kind of nibbles or snapshots of how the program operates, but we don’t really have an overall picture of what the numbers are,” says Andrew Crocker, a staff attorney at the Electronic Frontier Foundation.

Earlier this year, the NSA agreed to provide the public with some information about how many American citizens may be impacted, only to later walk back that promise. Director of National Intelligence Dan Coats explained the about face by saying that it “remains infeasible” for the government to cite a meaningful number.