The Constitution does not expressly grant the President additional war powers or other powers in times of national emergency. However, many scholars think that the Framers implied these powers because the structural design of the Executive Branch enables it to act faster than the Legislative Branch. Because the Constitution remains silent on the issue, the courts cannot grant the Executive Branch these powers when it tries to wield them. The courts will only recognize a right of the Executive Branch to use emergency powers if Congress has granted such powers to the President.
A claim of emergency powers was at the center of President Abraham Lincoln's suspension of habeas corpus without Congressional approval in 1861. Lincoln claimed that the rebellion created an emergency that permitted him the extraordinary power of unilaterally suspending the writ. With Chief Justice Roger Taney sitting as judge, the Federal District Court of Maryland struck down the suspension in Ex Parte Merryman, although Lincoln ignored the order. 17 F. Cas. 144 (1861).
President Franklin Delano Roosevelt similarly invoked emergency powers when he issued Executive Order 9066 directing that all Japanese Americans residing on the West Coast be placed into internment camps during World War II. Because Congress had already declared war, the U.S. Supreme Court found Congress to have recognized an ongoing emergency. Consequently, the President by issuing the order had acted in accordance with Congress's expressed intent, which was to respond to the emergency of war. For this reason, the U.S. Supreme Court upheld Executive Order 9066 in Korematsu v. United States as a constitutional exercise of Presidential Commander in Chief and emergency powers. 323 U.S. 214 (1944).
Harry Truman declared the use of emergency powers when he seized private steel mills that failed to produce steel because of a labor strike in 1952. With the Korean War ongoing, Truman asserted that he could not wage war successfully if the economy failed to provide him with the material resources necessary to keep the troops well-equipped. The U.S. Supreme Court, however, refused to buy the argument in Youngstown Sheet & Tube Co. v. Sawyer, voting 6-3 that neither Commander in Chief powers nor any claimed emergency powers gave the President the authority to unilaterally seize private property without Congressional legislation. 343 U.S. 579.