§ 144. As all persons and things within the territory of a State fall under its territorial supremacy, every State has jurisdiction over them. The Law of Nations, however, gives a right to every State to claim so-called exterritoriality and therefore exemption from local jurisdiction chiefly for its head,[231] its diplomatic envoys,[232] its men-of-war,[233] and its armed forces[234] abroad. And partly by custom and partly by treaty obligations, Eastern non-Christian States, Japan now excepted, are restricted[235] in their territorial jurisdiction with regard to foreign resident subjects of Christian Powers.
[231] Details below, §§ [348]-353, and [356].—The exemption of a State itself from the jurisdiction of another is not based upon a claim to exterritoriality, but upon the claim to equality; see above, § [115].
[232] Details below, §§ [385]-405.
[233] Details below, §§ [450]-451.
[235] Details below, §§ [318] and [440].
Jurisdiction over Citizens abroad.
§ 145. The Law of Nations does not prevent a State from exercising jurisdiction over its subjects travelling or residing abroad, since they remain under its personal supremacy. As every State can also exercise jurisdiction over aliens[236] within its boundaries, such aliens are often under two concurrent jurisdictions. And, since a State is not obliged to exercise jurisdiction for all matters over aliens on its territory, and since the home State is not obliged to exercise jurisdiction over its subjects abroad, it may and does happen that aliens are actually for some matters under no State's jurisdiction.
Jurisdiction on the Open Sea.