06/01/2015 05:59 EDT | Updated 06/01/2016 05:59 EDT

Expiry of controversial post-9-11 spy rules in U.S.: What happened, what's next?

WASHINGTON - Monday marked a milestone in the United States' fight against terrorism, with the expiry of several major provisions of the controversial 2001 Patriot Act.

Among the key changes: For the first time since the aftermath of the 9-11 attacks, Americans' phone records are no longer being systematically collected by the U.S. government.

That phone-metadata program operated in secrecy for years, before it was among the many surreptitious programs revealed to the world by the now-fugitive whistleblower Edward Snowden.

Time of death for the program: midnight, June 1, 2015. The cause? In part, it was done in by congressional paralysis.

Why did these provisions expire, and what's next?

Here's some background.

— What happened? To hear Rand Paul tell it, nothing less than the ideals of the American republic vanquishing tyranny: "A new day in America. A day with more liberty and freedom," the limited-government Kentucky senator tweeted, using the issue to promote his 2016 Republican presidential bid. He ran social-media ads requesting campaign donations, and sought signups on his website. Some of his big-military, pro-surveillance-state Republican colleagues were fuming. Critics accused him of grandstanding.

—What did Paul do? Lawmakers had until Monday to either create a new law or renew the old Patriot Act provisions before a sunset clause kicked in. The Senate found itself debating at the last minute whether to pass a bill supported by the White House and three-quarters of the House of Representatives, which would have reformed the data collection. With the clock ticking, the chamber's leadership sought a temporary extension of the old rules. But Paul denied the required consensus.

—What's changed? The National Security Agency immediately suspended its phone-metadata program. It's now harder for law enforcement to access business records like hotel and credit-card information, and obtain wiretaps for new investigations. Said White House spokesman Josh Earnest: "(This) introduces unnecessary risk to the country and our citizens."

—But does this really endanger Americans? The White House doesn't put it in terms quite that stark. For one thing, there's a grandfather clause; the old rules still apply for investigations already underway. There's also a bill before Congress. Plus, there's some debate about how useful the whole phone-data program actually was. An internal review by the Justice Department for 2007-2009 said investigators and federal lawyers viewed the act's controversial Section 215 as valuable in uncovering bits of information, but added that agents could not identify a major case development that resulted from it. One congressional defender linked the data collection to a foiled bomb plot against the New York and London subways in 2009, and a thwarted attack against a Danish newspaper.

—What happens next: Congress will consider a compromise bill. The House has already passed it. It would take the power to bulk-collect phone records away from government. Under that bill, the data would remain with phone providers — and the government would need a warrant to see it. The Obama administration supports the bill. The Senate will study it next. Earnest downplayed the civil-liberties risk of continuing to access phone data: "This is the information that you get in your monthly cellphone bill." The head of the Senate intelligence committee, Richard Burr, said it's simply used to see what phone numbers have called terrorist suspects, when those calls were made, and how long they lasted. "There is absolutely zero, zero content. There's zero identifier. There's not a person's name (attached)."