The Steamship Appam case in 1916 involved a British steamship that was captured by a German war vessel during World War I and brought to an American port. The owner of the ship, the British & African Steam Navigation Company Ltd., filed for its return under international law principles. However, the U.S District Court ruled in favor of Germany on grounds that it had jurisdiction over prizes brought into its ports voluntarily by captors during wartime. This decision was appealed to the Supreme Court which reversed it, ruling that although neutral countries have no obligation to restore prizes taken from their enemies at sea, they are not obliged either to allow such prizes remain within their territory or waters against their own consent expressed through laws or otherwise. Therefore, as per U.S neutrality laws prohibiting belligerent activities within its territories and waters including prize courts operations by foreign nations without express permission from Congress (which Germany did not have), Appam's capture was illegal and she should be returned back to her owners.

In the dissenting opinion for The Steamship Appam case, Justice Oliver Wendell Holmes disagreed with the majority's decision that British courts had jurisdiction over a German prize ship docked in an American port during World War I. He argued that international law did not support this conclusion and maintained that only the country where a prize is brought (in this case, America) has jurisdiction to adjudicate its status. Holmes believed it was inappropriate for Britain to exercise authority over a vessel located within U.S. territorial waters without consent from American authorities. He also expressed concern about potential diplomatic implications of allowing foreign powers to exert control within U.S borders, arguing such actions could undermine national sovereignty and potentially lead to conflict or war.