The Pesaro, a 1920 US Supreme Court case, revolved around the seizure of an Italian vessel during World War I by the United States. The ship was seized under the right of angary - a principle in international law that allows a belligerent nation to seize and use property belonging to neutrals within its jurisdiction if necessary for its self-preservation or war effort. After Italy entered into WWI on the side of Allied Powers, it sought compensation from U.S for this seizure. The court ruled against Italy's claim stating that since both countries were at war with Germany when the incident occurred, they should be considered as allies and thus no compensation was due. Furthermore, it held that even though there wasn't any formal declaration recognizing Italy as an ally at time of seizure; their common enemy made them de facto allies.

In the dissenting opinion for The Pesaro case in 1920, Justice Oliver Wendell Holmes Jr. argued that the majority's decision to allow a British ship seized during World War I by Italy to be returned was incorrect. He believed that it was not within the jurisdiction of U.S courts to decide on matters related to international law and war rights unless there were clear instructions from Congress or an executive agreement between nations involved. Furthermore, he stated that even if such authority existed, it should not have been exercised in this particular case because Britain had already accepted Italy's right over the vessel through diplomatic channels. Therefore, according to him, returning the ship would contradict established principles of international law and potentially harm relations with other countries.