The Schooner Exchange v McFaddon 11US 116 (Cranch)

A French naval vessel was put into Philadelphia for repairs after a storm. The libellants, John MacFaddon and other, who sought possession of the vessel claim that it was in reality the Schooner Exchange, seized by France on the High Seas in 1810 in accordance with a Napoleonic decree.

An appeal from the sentence of the Circuit Court of the US for the district of Pensylvania reversed the sentence of the District Court and ordered the vessel to be restores to the libellants [Immunity: par in parem non habet imperium] [This case assumes as general rule non-immunity, then qualifies it according to functional needs] [Immunity operates as bar in limine to proceedings, Act of State doctrine as a defence]

Resolution Marshall C.J.: The jurisdiction of the nation within its own territory is necessarily exclusive and absolute. All exceptions, therefore, to the full and complete power of a Nation within its own territories, must be traced up to the consent of the nation itself… either express or implied.

The world being composed of distinct sovereignties, possessing equal rights and equal independence, whose mutual benefit is promoted by intercourse … have consented to a relaxation in practice, in cases under certain peculiar circumstances, of that absolute and complete jurisdiction One sovereign being in no respect amenable to another, and being bound by obligations of the highest character not to degrade the dignity 1 [bases of immunity] of his nation, by placing himself or his sovereign rights within the jurisdiction of another, can be supposed to enter a foreign territory only under an express licence or in the confidence that the immunities belonging to his independent sovereign station, though not expressly stipulated, are reserved by implication, an will be extended to him.

This perfect equality 2 and absolute independence 3 of sovereigns, and this common interest impelling them to mutual intercourse, and an interchange of good offices with each other, [comity and reciprocity 4], have given rise to a class of cases in which every sovereign is understood to waive [of local sovereign 5] the exercise of a part of that complete exclusive territorial jurisdiction, which has been stated to be the attribute of every nation.

Why has the whole civilizes world concurred in this constructions? The answer cannot be a mistaken. A foreign sovereign is not understood as intending to subject himself to a jurisdiction incompatible with its dignity ‘it is impossible to conceive,’ says Vattel, ‘that a Prince who sends an ambassador or any other minister can have any intention of subjecting him to the authority of a foreign power … the latter, in receiving the minister, consents to admit him on the footing of independency’ As a public armed shipped acts under the immediate and direct command of a sovereign, the vessel was exempt from US jurisdiction.