 The Supreme Court decision in United States v. U.S. District Court (1972) left open the possibility for a foreign intelligence surveillance exception to the warrant clause. Three United States Courts of Appeals have recognized a foreign intelligence surveillance exception to the warrant clause, but tied it to certain requirements. The exception to the Fourth Amendment was formally recognized by the United States Foreign Intelligence Surveillance Court of Review in its 2008 In re Directives decision. The lower court held that, "a foreign intelligence exception to the Fourth Amendment's warrant requirement exists when surveillance is conducted to obtain foreign intelligence for national security purposes and is directed against foreign powers or agents of foreign powers reasonably believed to be located outside the United States." Despite the foregoing citation the Fourth Amendment prohibitions against unreasonable searches and seizures nonetheless apply to the contents of all communications, whatever the means, because, "a person's private communications are akin to personal papers." To protect the telecommunication carriers cooperating with the US government from legal action, the Congress passed a bill updating the Foreign Intelligence Surveillance Act of 1978 to permit this type of surveillance.
