Washington (CNN)Two years after Edward Snowden exposed the National Security Agency's secret collection of the data of millions of Americans' private communications, the bulk of those programs remain intact.
Everything you need to know about the Patriot Act debate
But the key section of the Patriot Act that the NSA used to authorize that program is set to expire on June 1.
Early Saturday morning, the Senate failed to pass both a two-month extension of the current program, as well as a House alternative that sought to keep many of the NSA's surveillance abilities intact. With the Senate set to take a week-long recess, Senate Majority Leader Mitch McConnell said the chamber will meet again on Sunday, May 31, to consider ways that would not let the program expire.
As the debate roils, get up to speed on NSA surveillance, how the Patriot Act authorized it and why Congress may -- or may not -- reform the program.
The law goes back to the 9/11 terrorist attacks and embodies the swift reaction of the executive and legislative branches in the wake of the deadliest terrorist strike on American soil.
Within weeks of the attacks, Congress passed and President George W. Bush signed the bill into law, giving law enforcement and intelligence authorities unprecedented domestic authority -- and the tools to wield that authority -- to thwart plots against the United States.
"Surveillance of communications is another essential tool to pursue and stop terrorists," Bush said at the law's signing ceremony in Oct. 2001. "The existing law was written in the era of rotary telephones. This new law that I sign today will allow surveillance of all communications used by terrorists, including emails, the Internet, and cell phones."
But it would end up doing much more -- more, even, than the law's major supporters and its primary architect on Capitol Hill, Wisconsin Republican Rep. Jim Sensenbrenner, ever imagined possible.
Yes, but the Patriot Act wasn't actually used for the justification for bulk metadata collection until 2006.
That practice began secretly in 2001 after Bush used his executive authority to give the NSA the green light to begin sweeping phone and Internet records after 9/11.
The Bush administration would eventually use the Patriot Act to justify its program -- enshrining it in law.
Metadata is all the information surrounding a call, including the caller's number, the receiver's number, the time and location of the call, and how long it lasted -- basically, everything except for the audio of the call itself. And the NSA collects the metadata of millions of Americans without those citizens' knowledge and without a warrant specifically targeting individuals suspected of wrongdoing.
The NSA can actually piece together quite a bit about a person by analyzing phone metadata --- information that a surveillance target's family might not even know.
Repeated calls to a cardiologist could suggest a heart condition. Repeated late night calls between two employees could suggest a romantic relationship.
"They can know, for example, whether an American called a psychiatrist three times in 36 hours, twice after midnight. That is a lot private information," explained Sen. Ron Wyden, D-Oregon, a leading supporter of NSA reforms.
And while NSA agents likely aren't spending their days poring over the metadata of Americans who aren't suspected of any terrorist activity, the agency does store the data for five years and retains easy access to the trove of information.
The government can petition the FISA court -- a secret court spawned out of the 1978 Foreign Intelligence Surveillance Act -- for a warrant to collect "any tangible things" to investigate terrorism or foreign spies.
If the government can credibly show that to the court's 11 judges, it gets a secret warrant that can force companies, such as Verizon, to hand over private information. And the recipient of the warrant is barred from discussing the warrant with anyone, due to national security concerns.
The Patriot Act stresses that the government can only request a warrant to obtain information that is "relevant to an ongoing investigation against international terrorism."
The Bush administration argued in 2006 that the metadata analysis program could only be successful if the government could collect and store the data of millions of Americans, even though it conceded "the vast majority of (data collected) will not be terrorist-related."
"Although admittedly a substantial portion of the telephony metadata that is collected would not relate to operatives of (redacted), the intelligence tool that the government hopes to use to find (redacted) communications -- metadata analysis -- requires collecting and storing large volumes of the metadata to enable later analysis. All of the metadata collected is thus relevant, because the success of this investigative tool depends on bulk collection," the administration argued.
That argument served as the justification for subsequent FISA court decisions approving warrants to collect customer data from various phone companies -- warrants that need to be renewed every 60 or 90 days.
That's right. But lawmakers who want changes to the program still have a tough slog ahead of them.
Sensenbrenner, the lead author of the Patriot Act, was quick to condemn the FISA court's interpretation of the law once Snowden revealed the extent of the dragnet surveillance, calling the practice "based on a blatant misreading of the law."
He and Sen. Patrick Leahy, D-Vermont, have since led the charge to reform the Patriot Act and their efforts have gained steam in recent months, with the USA Freedom Act overwhelmingly passing the House earlier this month in a 338-88 vote.
The reform bill would keep the government from collecting telephone metadata of millions of Americans, instead requiring the NSA to get a warrant from the FISA court to collect data on a specific individual from telecommunications companies.
But the law is facing stiff opposition in the Senate from some of that chamber's most powerful Republicans, including Senate Majority Leader Mitch McConnell, R-Kentucky, and the chairman of the Senate Intelligence Committee, Sen. Richard Burr of North Carolina, who want to reauthorize the Patriot Act for five years without any reforms.
And if the Senate can't reach an agreement to extend the Patriot Act in some way, chunks of the law would sunset on June 1.
Section 215, which authorizes the bulk metadata collection program, would sunset.
But two other sections of the Patriot Act would also expire: a so-called "lone wolf" provision and another section that allows roving wiretaps.
The first allows law enforcement to use the national security apparatus to go after suspected terrorists who may not be affiliated with a terrorist group, but share terrorist ideology and aims. That's a particular concern for law enforcement officials today as terrorist groups like ISIS are using social media to inspire individuals to carry out attacks in the U.S. and Europe.
The FBI would also lose the ability to apply for new roving wiretaps to pursue suspected terrorists, a common procedure used in other criminal investigations that allows officials to wiretap additional phones linked to a suspect without requesting a new warrant.
Former FBI Assistant Director Tom Fuentes, a CNN analyst, said losing that authority would be a "severe" blow to counterterrorism efforts, keeping the FBI from collecting the information it needs in a timely manner.
But counterterrorism officials already conducting investigations wouldn't be completely hamstrung. A provision in the Patriot Act would allow officials to use these tools in investigations that were started before the June 1 sunset date.
For opponents of reform, it's all about national security.
They cite the growing terror threats the U.S. is facing, as ISIS continues to grow in Syria and Iraq and expands its reach online, inspiring attacks in Europe and the U.S.
To throw away a key tool at a time of such heightened concern would be foolish, opponents say.
"For somebody to just say we're willing to let the Patriot Act expire is irresponsible," Republican Arizona Sen. John McCain, chairman of the Armed Services Committee, told CNN.
McCain and others argue that the U.S. could have prevented 9/11 if the NSA programs had been in place before the terror attacks.
And fellow Republican Sen. Lindsey Graham of South Carolina insisted that the NSA programs authorized under the Patriot Act are "still our best bet to prevent another 9/11."
"It's one thing to reform the Patriot Act," Graham said. "It's another thing to gut it or weaken it."
The Republican opponents of reform are toeing the line set out by Burr, the chairman of the Senate intelligence committee. Several Republican lawmakers -- including Graham and Sen. Thom Tillis of North Carolina -- cited Burr as their ideological guide on the Patriot Act and NSA surveillance.
"When Richard Burr tells me it goes too far, I think about that," Graham told CNN. "I trust his judgment."
Reformers insist their opponents are fear-mongering when there's actually little to fear from reforming domestic surveillance.
The government hasn't been able to provide any examples where the NSA's bulk data collection played a key role in thwarting a terror plot.
And multiple reviews of the program by groups and individuals with access to classified information have concluded the program isn't as much of a boon to national security as the staunchest defenders of the program suggest.
A presidential review group convened to review NSA surveillance in the wake of the Snowden revelations concluded "the information contributed to terrorist investigations by the use of Section 215 telephony meta-data was not essential to preventing attacks and could readily have been obtained in a timely manner using conventional Section 215 orders."
Put another way, the NSA doesn't need to pull telephone metadata on millions of Americans to protect U.S. national security -- it should just petition the FISA court for access to data of suspected terrorists.
The Privacy and Civil Liberties Oversight Board, an independent agency within the executive branch, also couldn't find "a single instance involving a threat to the U.S. in which the telephone records program made a concrete difference in the outcome of a counterterrorism investigation."
Richard Clarke, a former senior White House counterterrorism adviser to Republican and Democratic presidents who served on Obama's NSA review group, said "there's no way that you can claim that there's a single terrorist act that was prevented because of the telephony metadata collection program."
"There are always going to be politicians who take positions that are not fact-based but are based more on emotion and political positioning," Clarke said. "There are always going to be politicians who are going to position themselves as more opposed to terrorism than anybody else. But their positions are not analytically derived or fact-based."
Let's leave it to their own words. Here are several pro-reform lawmakers who sat down for interviews with CNN.
House Judiciary Committee Chairman Bob Goodlatte, R-Virginia, was one several top congressmen to meet with House Republican leadership to craft a compromise version of the USA Freedom Act that could pass the House.
"I think most Americans believe -- and I certainly do -- that you can have a very high level of protection of civil liberties and a very high level of national security. In fact, we believe this bill strengthens both," he said.
He noted that the bill would strengthen some provisions of the Patriot Act, ensuring, for example, that there is no lapse in surveillance between different agencies when a potential terrorist enters the U.S. and the FBI takes over -- without needing new authorization from the FISA court.
Sen. Mike Lee, the Republican from Utah who is sponsoring the USA Freedom Act in his chamber, is leaning his arguments on constitutional concerns and trust in government as he looks to sway conservatives.
"The USA Freedom Act does not propose that we abandon any and all efforts to analyze telephone data," Lee said. "What we're talking about here is a program that currently contemplates the collection of all data just as a routine matter and the aggregation of all that data in one database. That causes concerns for a lot of people... There's a lot of potential for abuse."
Reformers also point out that the FISA court is creating a body of what they call "secret law." The USA Freedom Act would require major FISA court decisions -- like the one that authorized bulk data collection -- be declassified.