Restrictions upon Territorial Supremacy.
§ 127. Just like independence, territorial supremacy does not give a boundless liberty of action. Thus, by customary International Law every State has a right to demand that its merchantmen can pass through the maritime belt of other States. Thus, further, navigation on so-called international rivers in Europe must be open to merchantmen of all States. Thus, thirdly, foreign monarchs and envoys, foreign men-of-war, and foreign armed forces must be granted exterritoriality. Thus, fourthly, through the right of protection over citizens abroad which is held by every State according to customary International Law, a State cannot treat foreign citizens passing through or residing on its territory arbitrarily according to discretion as it might treat its own subjects; it cannot, for instance, compel them to serve[202] in its army or navy. Thus, to give another and fifth example, a State, in spite of its territorial supremacy, is not allowed to alter the natural conditions of its own territory to the disadvantage of the natural conditions of the territory of a neighbouring State—for instance, to stop or to divert the flow of a river which runs from its own into neighbouring territory.[203]
[202] Great Britain would seem to uphold an exception to this rule, for Lord Reay, one of her delegates, declared—see "Deuxième Conférence Internationale de la Paix, Actes et Documents," vol. III. p. 41—the following at the second Hague Peace Conference of 1907: "Nous reconnaissons qu'en règle générale le neutre est exempt de tout service militaire dans l'Etat où il réside. Cependant dans les colonies britanniques et, dans une certaine mesure, dans tous les pays en voie de formation, la situation est tout autre et la population toute entière, sans distinction de nationalité, peut être appelée sous les armes pour défendre leurs foyers menacés."
In contradistinction to these restrictions by the customary Law of Nations, a State can through treaties enter into obligations of many a kind without thereby losing its internal independence and territorial supremacy. Thus France by three consecutive treaties of peace—namely, that of Utrecht of 1713, that of Aix-la-Chapelle of 1748, and that of Paris of 1763—entered into the obligation to pull down and not to rebuild the fortifications of Dunkirk.[204] Napoleon I. imposed by the Peace Treaty of Tilsit of 1807 upon Prussia the restriction not to keep more than 42,000 men under arms. Again, article 29 of the Treaty of Berlin of 1878 imposed upon Montenegro the restriction not to possess a navy.[205] There is hardly a State in existence which is not in one point or another restricted in its territorial supremacy by treaties with foreign Powers.
[204] This restriction was abolished by article 17 of the Treaty of Paris of 1783.
[205] It is doubtful whether this restriction is still in force; see below, § [258].
Restrictions upon Personal Supremacy.
§ 128. Personal Supremacy does not give a boundless liberty of action either. Although the citizens of a State remain under its power when abroad, such State is restricted in the exercise of this power with regard to all those matters in which the foreign State on whose territory these citizens reside is competent in consequence of its territorial supremacy. The duty to respect the territorial supremacy of a foreign State must prevent a State from doing all acts which, although they are according to its personal supremacy within its competence, would violate the territorial supremacy of this foreign State. Thus, for instance, a State is prevented from requiring such acts from its citizens abroad as are forbidden to them by the Municipal Law of the land in which they reside.
But a State may also by treaty obligation be for some parts restricted in the liberty of action with regard to its citizens. Thus articles 5, 25, 35, and 44 of the Treaty of Berlin of 1878 restrict the personal supremacy of Bulgaria, Montenegro, Servia, and Roumania in so far as these States are thereby obliged not to impose any religious disabilities on any of their subjects.[206]