(i)  Shared freshwater resources31

The term ‘international’ with reference to a body of water is merely a general indication of rivers and reservoirs which geographically and economically affect the territory and interests of two or more states. Conceivably a body of water could be ‘internationalized’, that is, given a status entirely distinct from the territorial sovereignty and jurisdiction of any state, on the basis of treaty or custom, general or regional. Rivers separating or traversing the territories of two or more states are usually subject to the territorial jurisdiction of riparian states up to the medium filum aquae, taken to beReferences(p. 338) the deepest channel of navigable waters or thalweg.32 But there are exceptions where some other boundary is agreed—for example the River San Juan, which forms part of the boundary between Nicaragua and Costa Rica, runs wholly in Nicaragua: the boundary is the right bank of the river on the Costa Rican side. However, the border treaty between the riparians also provides Costa Rica with a right of navigation on the San Juan ‘con objetos de comercio’.33 This right and its qualifier were considered in Navigational Rights, with the International Court determining, inter alia, that the phrase meant ‘for the purposes of commerce’, thereby ascribing to Costa Rica the right to carry goods and passengers on the river,34 as well as finding that persons so travelling were not required to obtain Nicaraguan visas or make payment to Nicaragua.35

The legal regime of rivers, creating rights for other riparians and non-riparian states and limiting the exercise of territorial jurisdiction for individual riparians, consists to a large extent of treaty law, and the International Court has focused on the terms of the particular treaty, making secondary reference to general international law or local cus-tom.36 Broadly, there are different legal regimes for navigational and non-navigational uses of rivers.37 The early assumption that navigational uses enjoyed primacy is no longer accurate; irrigation, hydro-electricity generation, and industrial uses are now more prominent in many regions than navigation, fishing, and floating of timber, and domestic use is growing rapidly.

Lac Lanoux concerned the interpretation of a treaty between France and Spain. However, the tribunal made observations on certain Spanish arguments based on customary law. On the one hand, the tribunal seemed to accept the principle that an upstream state is acting unlawfully if it changes the waters of a river in their natural condition in a way that could do serious injury to a downstream state. On the other, the tribunal stated that ‘the rule according to which States may utilize the hydraulic force of international watercourses only on condition of a prior agreement between the interested States cannot be established as a custom, or even less as a general principle of law’.38

References(p. 339) The issues of liability for changes in the flow of a river as between riparian states will be determined within the framework of the law of treaties in combination with the principles of state responsibility, as in Gabčíkovo-Nagymaros. At the same time the Court referred to the ‘basic right’ of Hungary ‘to an equitable and reasonable sharing of the resources of an international watercourse’.39 The case was in some respects special since a boundary river was involved.

In the case of navigable rivers it is accepted that customary law does not recognize a right of free navigation.40Only a minority of states have accepted the Barcelona Convention and Statute on the Regime of Navigable Waterways of International Concern of 1921,41 which provides for free navigation as between the parties on navigable waterways of international concern. Several treaty regimes for specific river systems provide for free navigation and equality of treatment for riparian states only.42 By contrast the treaty regime for the Danube has long conferred rights of navigation on non-riparians. The Belgrade Convention of 1948 maintained free navigation for all states whilst retaining powers of control for riparian states.43 Navigation by warships of non-riparian states is prohibited. In construing a treaty which creates machinery for supervision of an international regime of navigation, a tribunal may prefer not to employ a restrictive interpretation of the powers of the agency of control as against the territorial sovereigns.44

In the River Oder case, the Permanent Court, referring to the various conventions since the Act of the Congress of Vienna in 1815, stressed the ‘community of interest of riparian States’ which in a navigable river ‘becomes the basis of a common legal right, the essential features of which are the perfect equality of all riparian States in the use of the whole course of the river and the exclusion of any preferential privilege of any one riparian State in relation to the others’.45

In 1966 the International Law Association (ILA) adopted the Helsinki Rules on the Uses of Waters of International Rivers as a statement of existing international law covering both navigational and non-navigational uses.46 The ILA also adopted theReferences(p. 340) comprehensive revised Berlin Rules on Water Resources in 2004.47 The International Law Commission worked on the topic for over 20 years, culminating in the adoption of the Convention on the Law of Non-Navigational Uses of International Watercourses in 1997. Part II of the Convention sets out general principles for watercourses, including factors to be considered for ensuring equitable and reasonable utilization and participation, the avoidance of significant harm and how to remedy it, and general obligations of co-operation including sharing of information. Part III contains detailed provisions on prior notification of planned measures. In the absence of agreement no particular use of the watercourse enjoys inherent priority over others.48

A further advance occurred in Gabčíkovo-Nagymaros. There, the Court considered a dispute arising from a 1977 agreement between Czechoslovakia and Hungary to dam the Danube River in their respective territories in order to produce hydroelectric power in peaking mode. When Hungary refused to construct its dam due to environmental concerns, Slovakia diverted the river further onto its territory and built a second upstream dam—a contingency known as ‘Variant C’. The question was whether Slovakia was entitled to undertake Variant C despite the objections of its co-riparian. The Court noted that not only was the Danube a shared international watercourse, but also an international boundary river to which the principle of perfect equality between riparian states applied. Thus, by unilaterally diverting the Danube, Czechoslovakia assumed control of a shared resource and deprived Hungary of its right to a reasonable and equitable share thereof. In so deciding, the Court extended the principle in the River Oder case to non-navigational uses of watercourses.49

(ii)  International canals

Canals are in principle subject to the territorial sovereignty and jurisdiction of the state or states which they separate or traverse. Where the canal serves more than one state or otherwise affects the interests of more than one state a treaty regime may be created to regulate use and administration. The history of three canals of international concern has provided the basic materials for jurists seeking to establish general rules.

The Suez Canal was built and opened in 1869 under a private law concession for 99 years granted by the Egyptian government to the Universal Suez Maritime Canal Company. For most of its history the latter was a joint Franco-Egyptian company with aspects of its existence and functioning subjected to either French or Egyptian law. The British government was the largest shareholder. Eventually the affairs of the Canal were regulated by the Convention of Constantinople in 1888.50 Article I provided that the Canal ‘shall always be free and open, in time of war as in time of peace, to everyReferences(p. 341) vessel of commerce or of war, without distinction of flag’. The parties agreed not to interfere with the free use of the Canal and not to subject it to the right of blockade.

In 1954 Britain and Egypt agreed on British withdrawal from the Suez Canal base; the parties recognized that the Canal ‘which is an integral part of Egypt, is a waterway economically, commercially and strategically of international importance’.51 In 1956 the Egyptian government nationalized the Canal Company, under a law providing for compensation,52 but made no claim to alter the status of the Canal itself. Britain, France, and other states argued for the illegality of this measure, linking the status of the Company and the concession with the status of the Canal, and alleging that the nationalization was incompatible with the ‘international status’ of the Canal. As a result of the Franco-British invasion later in the same year Egypt abrogated the 1954 Agreement.53 On 24 April 1957 Egypt made a declaration confirming the rights and obligations arising from the Convention of Constantinople: the Declaration was registered under Charter Article 102, although in law it was a unilateral act.54

Until 1978 the Panama Canal Zone was occupied and administered by the US, independently of Panama, under the Hay–Bunau–Varilla Treaty of 1903,55 which provided that the Canal should be neutral in perpetuity and open to the vessels of all nations. Even before this, the Hay–Pauncefote Treaty had guaranteed free navigation, even in time of war, in terms borrowed from the Convention of Constantinople.56 But by a Treaty of 1977 (as amended in 1978), Panama was recognized as ‘territorial sovereign’ with rights of management of the Canal granted to the US for the duration of the Treaty.57

The Kiel Canal, though important for international commerce, was controlled by Germany untrammelled by special obligations until, in the Treaty of Versailles, it was provided that, except when Germany was a belligerent, the Canal was to be open to vessels of commerce and of war of all nations on terms of equality (Article 380). In 1936 the relevant provisions of the Treaty of Versailles were denounced by Germany, and other states seem to have acquiesced in this.58

It will be noted that this proposition was ancillary to an exercise in treaty interpretation and that even the general proposition depends on the incidence of ‘permanent dedication’. Moreover, interested states are reluctant to generalize: in 1956 the US regarded the Suez Canal as having an ‘international status’, while denying this in the case of the Panama Canal.60