Lawmakers are facing a potentially bruising fight over a surveillance law that expires Dec. 31 and must be extended in time to preserve what U.S. spy agencies consider a vital piece of their arsenal.

Congress has to extend the 2012 FISA Amendments Act, which will pit the Trump administration and national security hawks in Congress who favor a permanent reauthorization with no changes, against lawmakers of both parties, libertarians, privacy advocates and communications companies seeking to tighten protections for U.S. persons whose communications may get caught up in the wide electronic net cast by spy agencies.

The U.S. intelligence community, led by Director of National Intelligence Dan Coats, has staked out its position: a permanent reauthorization of the law without any changes. A bill sponsored by Sen. Tom Cotton, R-Ark., would do just that.

The legislation has the backing of 13 Republican senators, including Intelligence Chairman Richard M. Burr of North Carolina, Armed Services Chairman John McCain of Arizona and Lindsey Graham of South Carolina, a strong voice on national security matters.

Coats and Thomas P. Bossert, White House advisor on homeland security and counterterrorism, have said the existing law defends the United States from terrorism, weapons proliferation and foreign espionage, and therefore should be made permanent without any changes.

Those calling for reforms and tightening of privacy protections include the world’s top technology companies such as Amazon, Google, Facebook and Intel as well as privacy advocates and lawmakers of both parties.

Sunset Provision

Passage of any legislation will likely hinge on several key Republican lawmakers including, Sen. Rand Paul of Kentucky, who has consistently opposed surveillance programs, as well as lawmakers like Sen. Dean Heller of Nevada, who has called for greater transparency on surveillance programs.

It would also depend on key Democrats like Sen. Dianne Feinstein of California, the ranking member on the Judiciary committee, who also serves on the Intelligence committee. During a June hearing of the Judiciary committee, Feinstein said she favored a temporary extension of Section 702 of the FISA law.

“I believe any reauthorization should include a sunset provision, and without it, it will not have my support,” Feinstein said.

Asked on Sept.7 if she would back the privacy protections being sought by advocates, she said, “I haven’t really gotten into it yet so I don’t want to say what I’m for and what I’m not for.”

Judiciary committees in both chambers will work in close consultation with the intelligence committees to produce legislation extending the law. Senate Judiciary Chairman Charles E. Grassley, R-Iowa, already has gotten to work. Rep. Robert W. Goodlatte, R-Va., chairman of the House Judiciary Committee, said his panel is preparing a draft bill but declined to say when it would be ready.

House Judiciary “is working hard to achieve bipartisan consensus on FISA Section 702,” a committee aide said. “The goal is to ensure that both national security and Americans’ civil liberties are protected.”

Tense Debate

The 2012 FISA legislation allows U.S. spy agencies to conduct electronic surveillance on foreign persons. Section 702 of the act empowers the National Security Agency to collect and analyze emails and other digital communications of foreigners living overseas under a special court order, but the agency also ends up collecting data on an unknown number of U.S. persons, which it can later search without a warrant.

In 2012, NSA’s technologies capable of vacuuming up data from the internet backbone and service providers remained secret. And then came Edward Snowden, the government contractor who revealed the agency’s surveillance programs that collected U.S. phone call data and global internet traffic.

In the aftermath of Snowden’s revelations, the push to reauthorize the law is likely to cause friction.

“I think that we will address it before the end of the year,” said Rep. Trent Franks, R-Ariz., a member of the House Judiciary Committee. “We have debated this many times before and almost every time it comes up there’s a tense debate.”

The law itself was seemingly sound but had been administered differently in different administrations. “I’ve no problem with increasing the penalties or scrutiny toward those who would inappropriately administer the existing law. I’d want to be very careful about changing anything that weakened our security,” Franks added.

Backdoor Loophole

Reform advocates are seeking broader changes to outlaw specific kinds of intelligence collection techniques.

“A lot of us would object to requiring any keys to the backdoor,” said Rep. Eric Swalwell, D-Calif., who serves on both the House Judiciary and Intelligence committees. “We want to protect privacy of U.S. persons, but also make sure the intelligence community has the tools to protect the homeland. I think there’s a way to have a bipartisan consensus on this.”

Under the so-called backdoor search loophole, U.S. intelligence agencies including the NSA, CIA and FBI, can query data collected under Section 702 using a U.S. person’s identifier without first obtaining a court warrant. Privacy advocates say that provision circumvents the Fourth Amendment’s prohibition on unlawful search and seizure.

Privacy advocates are calling for four major changes: closing the loophole on U.S. person queries; a statutory end to so-called “about” collection, when NSA ends up with data that is neither to nor from a foreign target; limiting law-enforcement agencies’ use of data collected under Section 702; and limiting the scope of who can be targeted under the law.

Mission Creep

“The debate is not about keeping or killing Section 702,” said Jake Laperruque, a senior counsel at the Constitution Project. “It is about reforming 702 and curtailing mission creep and abuse, and any legislation that doesn’t include an end to backdoor search would have an extremely hard time passing.”

By ending the loophole, Laperruque wants to require intelligence and law enforcement agencies to obtain a court warrant before searching U.S. persons’ data.

An amendment sponsored by Reps. Thomas Massie, R-Ky., and Zoe Lofgren, D-Calif., to the Defense Department appropriations bill that passed the House in 2014 and 2015 with large majorities does just that: prevents the NSA from searching databases of online communications without first obtaining a probable cause warrant. But the amendment did not survive conference negotiations with the Senate.

Communications companies also are seeking to enshrine in law a prohibition on “about” collection even though the NSA said in May that it was ending the practice.

“Although the NSA has ceased the collection of ‘about’ data, we’d like that to be codified,” in law, said Bijan Madhani, senior policy counsel at the Computer & Communications Industry Association that represents all the major technology companies including Google, Amazon and Facebook.