The Fourth Amendment says they need "probable cause" of something, in order to "search and seize" our effects, or invade our space:
The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.
No worries the NSA is on the search for that "Probable Cause" ... or so a long trail of Haystack-sorters have told us over the years:
The NSA Is Building the Country’s Biggest Spy Center (Watch What You Say)
by James Bamford, wired.com -- 03.15.12
The software, created by a company called Narus that’s now part of Boeing, is controlled remotely from NSA headquarters at Fort Meade in Maryland and searches US sources for target addresses, locations, countries, and phone numbers, as well as watch-listed names, keywords, and phrases in email. Any communication that arouses suspicion, especially those to or from the million or so people on agency watch lists, are automatically copied or recorded and then transmitted to the NSA.
The scope of surveillance expands from there, Binney says. Once a name is entered into the Narus database, all phone calls and other communications to and from that person are automatically routed to the NSA’s recorders. “Anybody you want, route to a recorder,” Binney says. “If your number’s in there? Routed and gets recorded.” He adds, “The Narus device allows you to take it all.” And when Bluffdale is completed, whatever is collected will be routed there for storage and analysis.
The NSA also has the ability to eavesdrop on phone calls directly and in real time. According to Adrienne J. Kinne, who worked both before and after 9/11 as a voice interceptor at the NSA facility in Georgia, in the wake of the World Trade Center attacks “basically all rules were thrown out the window, and they would use any excuse to justify a waiver to spy on Americans.” Even journalists calling home from overseas were included. “A lot of time you could tell they were calling their families,” she says, “incredibly intimate, personal conversations.” Kinne found the act of eavesdropping on innocent fellow citizens personally distressing. “It’s almost like going through and finding somebody’s diary,” she says.
It's like looking for
There's "probable cause" in there -- somewhere.
Just give them time, they'll find it ...
But why should they bother though, the Patriotic Act has effectively nullified the need.
"Probable cause" generally refers to the requirement in criminal law that police have adequate reason to arrest someone, conduct a search, or seize property relating to an alleged crime.
Warrants and Probable Cause
Typically, to obtain a warrant, an officer will sign an affidavit stating the facts as to why probable cause exists to arrest someone, conduct a search or seize property. Judges issue warrants if they agree that probable cause exists.
There are many instances where warrants are not required to arrest or search, such as arrests for felonies witnessed in public by an officer. [...]
If a warrantless arrest occurs, probable cause must still be shown after the fact, and will be required in order to prosecute a defendant.
How quaint. Who needs "Probable Cause" when they have super-computers sleuthing-crimes, that are "probably" never wrong? Maybe. Most likely.
Best make hay, while the sun don't shine. There's LOTS of Haystacks out there, and they AREN'T going to sift themselves.