The Senate failed to pass legislation late Sunday to extend three Patriot Act surveillance measures ahead of their midnight expiration. The National Security Agency's bulk telephone metadata collection program—first exposed by Edward Snowden in 2013—is the most high-profile of the three spy tools whose legal authorization expired.

President Barack Obama was set to sign the bill, the USA Freedom Act, ahead of the midnight Sunday deadline. But Senate lawmakers who convened in a special session at 4pm ET Sunday could not reach an accord. The Senate is to resume debate Monday at noon ET.

As expected, there was much banter back and forth on the Senate floor about whether the Constitution was being gutted or whether the country would come to ruins if the Senate did not quickly adopt the already approved House legislation ahead of the June 1 expiration deadline. (The three Patriot Act provisions that failed to pass the Senate were renewed days ago in the House through 2019.)

"Are we willing to trade liberty for security?" asked Sen. Rand Paul (R-KY), perhaps the most vocal opponent of the legislation. Despite an apparent victory, Paul had no illusions that this fight for privacy would end after these specific extension talks. "The Patriot Act will expire tonight, but it will only be temporary," he added.

Sen. Dan Coats (R-IN) said it was time to stand up to terrorists and make "sure that we're doing everything we can to protect Americans from threats of people and a lot of organizations that want to kill us all, that would like to see us—see our heads on the chopping block."

After news of the imminent expiration broke, the American Civil Liberties Union quickly weighed in. "Congress should take advantage of this sunset to pass far-reaching surveillance reform, instead of the weak bill currently under consideration," the group said.

The three Patriot Act provisions on the agenda would have been extended until 2019 if approved. The first concerns the so-called "business records" provision that enabled the NSA's bulk telephone metadata program brought to light by the Snowden disclosures. This provision granted the government the power to seize all types of records—including those surrounding health and banking. The authorities must assert to the secret Foreign Intelligence Surveillance Act Court (FISA Court) that they are "relevant" to a terrorism investigation before getting a warrant. The bulk metadata collection program was altered somewhat under the House and Senate legislation, however.

Under the package, the bulk metadata would have stayed with the telecoms. The authorities could then search the data with a FISA Court warrant, and the nation's spies must articulate a reasonable suspicion that the phone data is relevant to a terror investigation and that at least one party to the call is overseas. Under the provision, the Constitution's Fourth Amendment standard of probable cause does not apply. The metadata includes phone numbers of all parties in a call, numbers of calling cards, time and length of calls, and the international mobile subscriber identity (ISMI) of mobile calls.

The second provision that expired Sunday is lesser known and involves roving wiretaps. Under these wiretaps, the authorities may tap a terror suspects' communications even as they hop from one device to the next. Agents don't even need to tell the FISA Court who they are targeting, although a warrant from that court is required.

The last surveillance tool that failed to win Senate approval is the "lone wolf" provision. This allows the same type of roving wiretap authority, but the suspect does not have to be linked to terrorism or a foreign power.

Listing image by Kim Davies