NSA Domestic Spying Program May Expire: What to Know

Certain provisions of the Patriot Act, including those the National Security Agency uses for the controversial bulk collection of Americans' phone records, will expire when the clock strikes midnight on June 1 if Congress can't reach an agreement about the future of the program.

Lawmakers are at odds over whether and how the controversial practice should continue, and with the expiration deadline approaching, the White House has warned of the national security impact shuttering the program will have, potentially cause law enforcement officials to lose important tools to help them track down and prosecute suspected terrorists unless legislation is passed.

The fate of the program will unfold on the Senate floor Sunday afternoon. Here's what you need to know about the debate over the NSA and the Patriot Act.

WHAT EXACTLY IS EXPIRING?

Several provisions of the Patriot Act will expire at midnight on June 1st. The one you've probably heard about the most is Section 215, which provides the authority for the NSA's bulk collection of Americans' phone records. That's the controversial program first exposed by NSA contractor Edward Snowden in 2013. This allows the NSA to access telephony metadata -- basically information about where, when and to whom calls were made, but recordings of the calls themselves.

It also includes a provision that allows prosecutors to collect other information, like business records, on suspected terrorists by acquiring a court order. Section 215 is used in terrorism cases about 200 times a year, according to senior administration officials.

But there are two other, lesser-known programs that also face the June 1st expiration deadline. One allows law enforcement officials to use roving wiretaps to monitor individuals using different phones, a power that is exercised less than 100 times a year. The other is the so-called "Lone Wolf" provision which allows officials to monitor a suspected terrorist even if they can't establish any ties to a known terrorist organization. While this power has never been used, senior administration officials say it could be valuable in the future in detecting people planning terror attacks as lone wolves.

WHAT IS CONGRESS FIGHTING ABOUT?

There are several camps involved in the fight over the Patriot Act. There are those - like Senate Majority Leader Mitch McConnell and Senator Richard Burr - who wanted to extend the program without any changes.

Then there are the supporters of the USA Freedom Act, which passed the House of Representatives with a vote of 303-121, and has support from lawmakers like Sens. Patrick Leahy, ranking member of the Senate Judiciary Committee, Ted Cruz, R_Texas, and Mike Lee, R-Utah. The NSA would have to obtain a warrant from the U.S. Foreign Intelligence courts in order to query the information from the database.

Finally, there are those like Sen. Rand Paul, R-Kentucky, who want to end the collection of phone records completely and allow the provisions to run out. Paul even spoke on the Senate floor for ten and a half hours protesting the Patriot Act, and a super PAC supporting Paul, America's Liberty, has released a web ad teeing up Paul's upcoming stand against the NSA on Sunday.

WAIT, THERE'S A WRESTLING MATCH IN THE SENATE SUNDAY?

No - but the fate of the program NSA's domestic surveillance program could be determined on Sunday.

Here's where things stand: While the Republican controlled House passed the USA Freedom Act earlier this month, it faced opposition as soon as it arrived in the Senate, especially as the upper chamber's top Republican leader, Senator Mitch McConnell, pushed his colleagues for a blank extension of the surveillance program.

With Memorial Day recess looming, the Senate voted on the USA Freedom Act in the early morning hours last Saturday, but fell three votes short of clearing a key procedural hurdle. Shortly after some political theatrics on the Senate floor, the upper chamber voted to block a two month extension of the Patriot Act to give lawmakers time to hammer out a compromise.

The Senate then adjourned for the week and senators are slated to return at 4:00 p.m. Sunday, with only eight hours left until the program expires.

SO THE PROGRAM MAY END AT MIDNIGHT ON JUNE 1?

Actually, the process to end the program starts much earlier than midnight, according to senior administration officials The NSA will begin shutting down the surveillance system at 4:00 p.m. on Sunday if Congress has not passed legislation by then.

The NSA then has until 8:00 p.m. to cancel the shutdown. At that point, it is irreversible. Once the database is shut down, it would take an entire day to restart the system. No additional metadata could be collected while the system is down nor would law enforcement officials be able to search the database.

Lawmakers are in negotiations to find an agreement before the Senate returns on Sunday, but unless the Senate passes legislation by 8:00 p.m. on Sunday, the surveillance program is expected to go dark for at least a few days, which President Obama has warned lawmakers about.

"The House of Representatives did its work which strikes the appropriate balance," Obama said this week. "The Senate did not act...I strongly urge the Senate to work through this recess and make sure that they identify a way to get this done."

"This needs to get done," he added.