This paperback, break-out edition, which focuses solely on national security law, is derived from the popular and seminal casebook, Foreign Relations and National Security Law (4th ed. 2012). Full treatment is given to the nature and structure of the field, the war power, the power of the purse, the investigation and prosecution of threats to national security, and the control of information relating to national security. Key issues concerning customary international law and treaties as sources of law in the United States are covered, but less than in the hardback edition. Issues relating to federalism are not addressed.