# Prize Cases *The Brig Amy Warwick*, 67 U.S. (2 Black) 635 (1863) — the consolidated Supreme Court decision upholding Abraham Lincoln's blockade of Confederate ports, imposed by proclamation in April 1861 while Congress was out of session and before any congressional authorization existed. Shipowners whose vessels had been seized as prizes argued that a blockade is an act of war, that only Congress can initiate war, and that the seizures were therefore unlawful. The Court agreed with the premise and split 5–4 on the conclusion. Justice Grier's majority accepted that a blockade is an act of war and that the President "has no power to initiate or declare a war," but held that when war is thrust upon the nation the President is "bound to resist force by force" without waiting for Congress — and that Congress's July 1861 ratifying statute cured any defect. The case is cited on both sides of modern war powers disputes: for the proposition that a President may respond to a sudden attack unilaterally, and — the point that matters in [[War Powers Decision Flow]] — for the settled premise that **a blockade is an act of war**, which complicates any claim that a blockading force is not engaged in hostilities.