50 USC § 1844. 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.
(Pub. L. 95–511, title IV, §404, as added Pub. L. 105–272, title VI, §601(2), Oct. 20, 1998, 112 Stat. 2408.)