Exiled U.S. whistleblower and former National Security Agency contractor Edward Snowden on Tuesday called out years of impunity for the NSA violating Americans' civil liberties and privacy rights.

Snowden's tweet came in response to CNN reporting that the NSA "failed to follow both court-approved and internal procedures designed to prevent officials from using a controversial foreign surveillance law to inappropriately monitor Americans' communications."

The revelations related to Section 702 of the Foreign Intelligence Surveillance Act (FISA) came in a new semi-annual government watchdog report to Congress. Snowden highlighted that such failures at the NSA are part of a long trend of abuse.

"This has happened year after year since the program began," said Snowden, who has lived in Russia since exposing U.S. government mass surveillance in 2013. Asked by one Twitter user about the penalties for the agency's conduct, he added that "there aren't any."

The controversial law, which enables the U.S. government to collect communications of foreigners located outside the United States without warrants, "broadly prohibits the intelligence community and law enforcement from targeting U.S. persons," CNN explained. However, a loophole allows for warrantless searches of "702-gathered information for Americans' records if 'a query is reasonably likely to return foreign intelligence information.'"

Privacy advocates have long called on Congress to close this "backdoor search" loophole. More than two dozen groups wrote to lawmakers last summer that "ending this unconstitutional practice is imperative to ensure that foreign intelligence surveillance does not swallow Americans' privacy rights."