Last month, Director of National Intelligence James Clapper sent a letter to Oregon Sen. Ron Wyden admitting that the NSA and CIA used a loophole to search the emails and other electronic communications of Americans without a warrant. Clapper defended the searches as legal.
"As you know, when Congress reauthorized Section 702, the proposal to restrict such queries was specifically raised and ultimately not adopted," Clapper wrote in the letter, referring to a 2011 rule change to the FISA Amendments Act. From the New York Times:
A 2008 law, the FISA Amendments Act, legalized the warrantless surveillance program that the Bush administration created after the terrorist attacks of Sept. 11, 2001. The law permits the government to intercept phone calls and emails without a warrant and on domestic soil, as long as the surveillance target is a noncitizen who lives abroad.
In fall 2011, the Obama administration obtained the approval of the Foreign Intelligence Surveillance Court for analysts to search for "U.S. person identifiers" in the repository, enabling them to pull out phone calls and emails involving Americans that had been intercepted because the people involved had been in contact with a foreign target.
Sen. Wyden, who has been one of the NSA spying program's strongest critics, called the tactic "unacceptable."
"It is now clear to the public that the list of ongoing intrusive surveillance practices by the NSA includes not only bulk collection of Americans' phone records, but also warrantless searches of the content of Americans' personal communications," Wyden said in a joint statement with Sen. Mark Udall. "Senior officials have sometimes suggested that government agencies do not deliberately read Americans' e-mails, monitor their online activity or listen to their phone calls without a warrant. However, the facts show that those suggestions were misleading, and that intelligence agencies have indeed conducted warrantless searches for Americans' communications using the 'back-door search' loophole in section 702 of the Foreign Intelligence Surveillance Act."
The "back-door search" was first revealed last August by the Guardian, who based their report on documents provided by Edward Snowden.