Paris, Declaration of, April 16, 1856, an agreement on international maritime law signed by the major European powers and ratified by almost all nations. The declaration (1) established that privateers are illegal; (2) laid down certain conditions under which neutral shipping is not liable to capture in wartime; and (3) set forth the principle that a blockade, in order to be legal, must be effective (that is, there must be close control of an enemy's ports by ships stationed just offshore).
The United States objected that it would need privateers in wartime to supplement its navy and therefore did not ratify the treaty. Actually, however, the United States never again employed privateers. (The Confederacy, during the American Civil War, briefly experimented with privateering but with little success.) World War I, which saw violations of the blockade and neutrality provisions, demonstrated that naval warfare had so changed that the Declaration was no longer applicable.
