50 U.S.C. § 1844 : War And National Defense — Foreign Intelligence Surveillance — Pen Registers And Trap And Trace Devices For Foreign Intelligence Purposes — Authorization During Time Of War

Notwithstanding any other provision of law, the President, through the Attorney General, may authorize the use of a pen register or trap and trace device without a court order under this subchapter to acquire foreign intelligence information for a period not to exceed 15 calendar days following a declaration of war by Congress.