In the Prize Cases (67 U.S. (2 Black) 635), President Lincoln established a blockade of southern ports during the Civil War. People sued, claiming that the President did not have the authority to issue such an order. However, the Supreme Court found the blockade to be a constitutional exercise of the President's authority under the War Powers Act. The Court came to this conclusion even though a formal war declaration was never issued. "As a Civil War is never publicly proclaimed, its actual existence is a fact in our domestic history which the Court is bound to notice and to know." The Court also recognized that Congress couldn't technically declare war against a US State anyway, so there couldn't be a declaration of war.