Respondent Jose Padilla is a United States citizen detained by the Department of Defense pursuant to the President's determination that he is an "enemy combatant" who conspired with al Qaeda to carry out terrorist attacks in the United States. We confront two questions: First, did Padilla properly file his habeas petition in the Southern District of New York; and second, did the President possess authority to detain Padilla militarily. We answer the threshold question in the negative and thus do not reach the second question presented.