Congress is under the gun to reauthorize a major surveillance law in a debate that has been overshadowed by other major policy fights, like net neutrality and the investigation into online Russian election meddling.

Why it matters: The law — known as Section 702 — expires at the end of the year. Intelligence agencies say it would be ultimately catastrophic if it isn't reauthorized. Privacy-minded lawmakers and advocates, however, say that if it is reauthorized without reforms it will perpetuate a sprawling surveillance system that ensnares Americans' information without a warrant.

What the law does

The law is used by the intelligence community to justify the warrantless surveillance of the electronic communications of foreign nationals located abroad.

The debate

Those agencies have pushed aggressively to renew the law without any reforms. But privacy advocates inside and outside of government say that the programs under the law pick up communications belonging to Americans, too.

They've also raised concerns about the way information obtained without a warrant under the law can be used by the FBI in criminal – rather than national security – cases.

What's next?