The London Declaration concerning the Laws of Naval War is an international code of maritime law, especially as it relates to wartime activities, proposed in 1909 at the London Naval Conference by the leading European naval powers, as well as the United States and Japan, after a multinational conference that occurred in 1908 in London. Although it dealt with many controversial points, including blockades, contraband and prize, it largely reiterated existing law, although it showed greater regard to the rights of neutral entities. The declaration was ratified by the United States Senate, but not by many other powers; it never went into effect officially.
The United States insisted that the belligerent nations fighting in World War I abide by the Declaration. Both the British and Germans ignored it.