The reauthorization of Section 702 of the Foreign Intelligence Surveillance Act will pit civil liberties advocates who oppose the warrantless eavesdropping authority it provides, against law enforcement agencies that say it’s crucial to their efforts to combat terrorism.

The provision allows law enforcement to snoop on the communications of foreigners believed to be overseas, although American officials acknowledge that the communications of Americans are sometimes swept up as well — something known as “incidental collection.”

The Office of the Director of National Intelligence said last month that renewing Section 702 is its top legislative priority for 2017.

At a May 11 hearing before the Senate Intelligence Committee, Director of National Intelligence Dan Coats called Section 702 “an extremely effective tool to protect our nation from terrorist and other threats.”

The program will expire at the end of the year unless Congress acts to renew it. The battle could track the one that occurred in 2015 over the Patriot Act authority that allowed the government to collect meta-data about Americans’ phone calls, such as their length and the numbers involved. Civil libertarians won that battle when Congress passed a new law barring the government from holding the data. It must now request it from phone companies on an as-needed basis.

At the May 11 hearing, National Security Agency Directory Adm. Michael Rogers explained what the impact would be on U.S. intelligence agencies and law enforcement if they lose 702’s authorities.

“We would be significantly degraded in our ability to provide timely warning and insight as to what terrorist actors, nation states, criminal elements are doing that is of concern to our nation as well as our friends and allies,” Rogers said. “This 702 has provided us insight that is focused both on counterterrorism, but as well as counter proliferation, understanding what nation states are doing.”