Prize Cases

The Prize Cases referred to the adjudication during the American Civil War of four captures of ships which had violated the blockade of the South by the Union Navy. The cases raised questions which could have worked against the Union war effort. The Supreme Court's ruling supported the Union position, establishing the right of a government to set up a blockade of its own ports during an insurrection, and establishing the right of the president to set up the blockade without a declaration of war by Congress. The issue in international law was complicated by the fact that the Union did not want to treat the Confederacy as an international belligerent or give it belligerent status, while at the same time the Union sought to close the ports of the South by blockade. Since blockades can only be used against belligerents, the Union appeared to want to have it both ways.

In the Prize Cases, if the courts ruled that a blockade existed, foreign powers might regard that as recognition of the status of the Confederacy as a belligerent state. However, if the courts ruled that the blockade was not legal, then the power of the president to conduct the war through seizure of merchant ships carrying arms and other contraband to the Confederacy would be impaired.