Side by side with these general treaties, which recognise free navigation on international rivers, stand treaties[302] of several South American States with other States concerning free navigation for merchantmen of all nations on a number of South American rivers. And the Arbitration Court in the case of the boundary dispute between Great Britain and Venezuela decided in 1903 in favour of free navigation for merchantmen of all nations on the rivers Amakourou and Barima.
[302] See Taylor, § 238, and Moore, I. § 131, pp. 639-651.
Thus the principle of free navigation, which is a settled fact as regards all European and some African international rivers, becomes more and more extended over all other international rivers of the world. But when several writers maintain that free navigation on all international rivers of the world is already a recognised rule of the Law of Nations, they are decidedly wrong, although such a universal rule will certainly be proclaimed in the future. There can be no doubt that as regards the South American rivers the principle is recognised by treaties between a small number of Powers only. And there are examples which show that the principle is not yet universally recognised. Thus by article 4 of the Treaty of Washington of 1854 between Great Britain and the United States the former grants to vessels of the latter free navigation on the river St. Lawrence as a revocable privilege, and article 26 of the Treaty of Washington of 1871 stipulates for vessels of the United States, but not for vessels of other nations, free navigation "for ever" on the same river.[303]
[303] See Wharton, pp. 81-83; Moore, I. § 131, p. 631, and Hall, § 39.
However this may be, the principle of free navigation embodies the rule that vessels of all nations must be admitted without payment of any dues whatever. Yet this principle does not exclude the levy of dues from all navigating vessels for expenses incurred by the riparian States for such improvements of the navigability of rivers as embankments, breakwaters, and the like.[304]
[304] As regards the question of levying dues for navigation of the rivers Rhine and Elbe, see Arndt in Z.V. IV. (1910), pp. 208-229.
I should mention that the Institute of International Law, at its meeting at Heidelberg in 1888, adopted a Projet de Règlement international de navigation fluviale,[305] which comprises forty articles.
[305] See Annuaire, IX. p. 182.
Utilisation of the flow of rivers.
§ 178a. Apart from navigation on rivers, the question of the utilisation of the flow of rivers is of importance. With regard to national rivers, the question can not indeed be raised, since the local State is absolutely unhindered in the utilisation of the flow. But the flow of not-national, boundary, and international rivers is not within the arbitrary power of one of the riparian States, for it is a rule of International Law[306] that no State is 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 this reason a State is not only forbidden to stop or to divert the flow of a river which runs from its own to a neighbouring State, but likewise to make such use of the water of the river as either causes danger to the neighbouring State or prevents it from making proper use[307] of the flow of the river on its part. Since, apart from special treaties between neighbouring countries concerning special cases, neither customary nor conventional detailed rules of International Law concerning this subject are in existence, the Institute of International Law, at its meeting at Madrid[308] in 1911, adopted the following "Réglementation internationale des cours d'eau internationaux au point de vue de leur force motrice et de leur utilisation industrielle ou agricole":—