While the fact of NSA surveillance catching U.S. citizens in its dragnets has been in the public domain since last summer (thanks to leaks from Edward Snowden), the intelligence community has withheld officially admitting that it has warrantlessy spied on Americans. National Intelligence director James Clapper went so far as to lie to Congress on the matter.
However, in response to repeated decrials from Congress' premier privacy advocate, Oregon Democrat Sen. Ron Wyden, Clapper has finally officially admitted that the NSA used a "back door" in surveillance law to perform warrantless searches on Americans’ communications. In a letter to Wyden, obtained by the Guardian, Clapper wrote:
There have been queries, using U.S. person identifiers, of communications lawfully acquired to obtain foreign intelligence targeting non-US persons reasonably believed to be located outside the United States.
These queries were performed pursuant to minimization procedures approved by the Fisa court and consistent with the statute and the fourth amendment.
Clapper's reference to the lawfulness of such surveillance will rankle NSA critics. The shady FISA court law to enable such surveillance has been widely criticized as a dangerous legal loophole, secretly opened by the shady spy court to enable in the letter of the law an invasion of Americans' privacy, which -- while post hoc FISA court permitted in the age of post-9/11 national security paranoia -- is a far cry from the spirit of constitutional protections.