Updated at 11 a.m. ET
Beginning this week, members of Congress intend to get answers from the National Security Agency about the legal justification it's been relying on for its sweeping surveillance activities. Congress will get its chance to question the intelligence community with a series of briefings and at least two hearings this week, while a few members will meet Tuesday to consider a possible lawsuit in response to the surveillance revelations.
"I think it's a constitutional issue, without a doubt," Rep. Thomas Massie, R-Ky., said to CBSNews.com about the NSA's recently revealed tactics, which include the widespread collection of U.S. phone records from Verizon, as well as the collection of internet content from non-U.S. internet users outside of the United States. While the collection of internet content doesn't target U.S. users, the NSA could capture information from Americans unintentionally.
"I don't think the Constitution allows for broad sweeps of personal data of people who aren't even suspected of doing anything," Massie said. "As of this week, we now know that's occurring."
Massie said he's meeting Tuesday with Rep. Justin Amash, R-Mich., and Sen. Rand Paul, R-Ky. -- two other civil liberties advocates -- to discuss a possible lawsuit on the matter, though he declined to go into more detail.
On Fox News Sunday over the weekend, Paul said, "I'm going to be seeing if I can challenge this at the Supreme Court level. I'm going to be asking all the internet providers and all of the phone companies: Ask your customers to join me in a class action lawsuit. If we get 10 million Americans saying we don't want our phone records looked at, then maybe someone will wake up and something will change in Washington."
While the breadth of the NSA's surveillance is broad -- and some say unconstitutional -- many lawmakers and experts say it has a basis in the sweeping surveillance measures passed by Congress in the Patriot Act and 2008 FISA Amendments Act (which amended the Foreign Intelligence Surveillance Act).
The FISA Amendments Act was challenged in the Supreme Court as recently as last year in Clapper v. Amnesty International USA. In that case, plaintiffs including lawyers and journalists sued, arguing their communications with foreign contacts were targeted by the U.S. government. In its ruling this year, the court essentially punted on the case, arguing the plaintiffs had no standing (in other words, that the plaintiffs had no proof that they were either the targets of surveillance or would be in the future).
Clapper was a serious blow to privacy advocates, but with the new revelations of government surveillance, "the landscape for standing... has changed significantly," Loyola Law School professor Karl Manheim, an expert on constitutional law and privacy, told CBSNews.com.
"Ordinarily, a lower court would be bound by the Clapper decision and the case would be dismissed," he said. However, "since there doesn't seem to be any lack of people who have been injured by these programs, a different set of plaintiffs could sue."
While a court challenge may or may not be in the future, members of Congress are at least looking for a fuller explanation of the NSA's interpretation of the Patriot Act and the FISA Amendments Act.
The full House of Representatives will get an NSA briefing Tuesday afternoon, while the House Intelligence Committee will get another briefing on Thursday. The Senate Intelligence Committee will hold another briefing on details of the NSA programs, open to all members of the U.S. Senate, on Thursday.
Massie and 22 other members of Congress put their questions for the NSA and the FBI in writing last week, asking the agencies to clarify their position on the Patriot Act.
Massie suggested while the NSA's activities may technically fall under the authority granted by the Patriot Act or the FISA Amendments Act, the laws are being used in ways they shouldn't be.
"Whether those laws authorize them or not, when those laws were passed, those of us complaining about them were assured, 'Oh, that's not what this is about,'" he said of the privacy concerns. "What we're finding out is it's about getting everybody's data."
Some privacy advocates, however, contend that the NSA's broad surveillance tactics aren't even legal by the standards of the Patriot Act or the FISA Amendments Act.
The Electronic Privacy Information Center (EPIC) last week asked different congressional committees to hold hearings on the legality of the NSA programs, arguing the FISA court that issued the Verizon order "went beyond its legal authority when it sanctioned a program of domestic surveillance unrelated to the collection of foreign intelligence."
"I couldn't believe that the FISA court would issue such an order," EPIC executive director Marc Rotenberg told CBSNews.com. "It's really almost unimaginable."
The Senate Appropriations Committee will have the first crack at questioning the intelligence community, when NSA Director Keith Alexander testifies on Wednesday during a previously-scheduled hearing. Committee chairwoman Sen. Barbara Mikulski, D-Md., will likely have pointed comments for Alexander as she did last week for Attorney General Eric Holder during his appearance before the committee.
She urged more transparency with Congress on surveillance programs and criticized repeated statements that lawmakers have been "fully briefed" on these programs.
"This 'fully briefed' is something that drives us up the wall," Mikulski said. "'Fully briefed' doesn't mean we know what's going on."
On Thursday, FBI director Robert Mueller is sure to be grilled when he testifies to the House Judiciary Committee. "I am very concerned that the Department of Justice may have abused the intent of the law and we will investigate that and whether the law needs to be changed as a result," Committee Chairman Bob Goodlatte, R-Va., said in a statement last week, adding that he intends to raise the matter with Mueller.
Outside groups, meanwhile, are also seeking further explanation for the legal basis for these programs. On Monday, the American Civil Liberties Union (ACLU) and the Media Freedom and Information Access Clinic at Yale Law School filed a motion with the FISA court, requesting it publish its opinions on the meaning, scope and constitutionality of the relevant parts of the Patriot Act. The Electronic Frontier Foundation (EFF) is also seeking to unseal any FISA court orders declaring the NSA surveillance programs unconstitutional -- the secret court gave at least one such order.
The Foreign Intelligence Surveillance Court -- which has approved nearly every government request -- does not make its opinions public. Manheim said he knew of only one unsealed opinion.
On Tuesday, a bipartisan group of senators -- Sens. Jeff Merkley, D-Ore., Mike Lee, R-Utah; Patrick Leahy, D-Vt; Dean Heller, R-Nev.; Mark Begich, D-Alaska; Al Franken, D-Minn; Jon Tester, D-Mont.; and Ron Wyden, D-Ore. -- introduced a bill that would require the Attorney General to declassify significant Foreign Intelligence Surveillance Court opinions.
Before last week's revelations, Congress didn't seem too concerned about potential invasions of privacy by the intelligence community. In April, over the objections of the White House and privacy advocates, the House, which would encourage companies to share information collected on the internet with the federal government.
However, EPIC's Rotenberg thinks the latest revelations will spur some legislative changes. "I wouldn't say Congress is near rebellion yet, but people are really not happy," he said. "I suspect even members of the intelligence committee are troubled now, as they think about the full implications of what they may have allowed to happen... It was a mistake not to adopt better oversight mechanisms, more public reporting, to release some of the [FISA] court's opinions."