This fully updated Fourth Edition of a seminal casebook contains classic cases from Foster v. Nielsen to Samantar v. Yousuf, penetrating commentary from The Federalist to Dean Harold Koh and Justice Antonin Scalia, and treatment of thought-provoking controversies, including intervention in Libya, Wikileak disclosures, the killing of Bin Laden, drone attacks on U.S. nationals, NSA wiretapping, and Guantnamo trials. Excerpts of treaties, statutes, and executive orders address the core doctrinal and theoretical issues of foreign relations law and national security law, providing ample room for professors to design a course based on those topics most suited for their classroom experience.