State responsibility Hungary’s actions in refusing to complete the Project amounted to an unjustified breach of the Treaty on the Construction and Operation of the Gabčíkovo-Nagymaros Barrage System of 1977, went on to say: In the view of the Court, an important consideration is that the effects of a countermeasure must be commensurate with the injury suffered, taking account of the rights in question. In 1929, the Permanent Court of International Justice, with regard to navigation on the River Oder, stated as follows: “[the] community of interest 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 user [sic] of the whole course of the river and the exclusion of any preferential privilege of any one riparian State in relation to the others”... Modern development of international law has strengthened this principle for non-navigational uses of international watercourses as well ... The Court considers that Czechoslovakia, by unilaterally assuming control of a shared resource, and thereby depriving Hungary of its right to an equitable and reasonable share of the natural resources of the Danube—with the continuing effects of the diversion of these waters on the ecology of the riparian area of the Szigetköz—failed to respect the proportionality which is required by international law ... The Court thus considers that the diversion of the Danube carried out by Czechoslovakia was not a lawful countermeasure because it was not proportionate. Thus, the Court took into account the quality or character of the rights in question as a matter of principle and (like the tribunal in the Air Service Agreement case) did not assess the question of proportionality only in quantitative terms. (5) In other areas of the law where proportionality is relevant (e.g. self-defence), it is normal to express the requirement in positive terms, even though, in those areas as well, what is proportionate is not a matter which can be determined precisely.783 The positive formulation of the proportionality requirement is adopted in article 51. A negative formulation might allow too much latitude, in a context where there is concern as to the possible abuse of countermeasures. (6) Considering the need to ensure that the adoption of countermeasures does not lead to inequitable results, proportionality must be assessed taking into account not only the purely “quantitative” element of the injury suffered, but also “qualitative” factors such as the importance of the interest protected by the rule infringed and the seriousness of the breach. Article 51 relates proportionality primarily to the injury suffered but “taking into account” two further criteria: the gravity of the internationally wrongful act, and the rights in question. The reference to “the rights in question” has a broad meaning, and includes not only the effect of a wrongful act on the injured State but also on the rights of the responsible State. Furthermore, the position of other States which may be affected may also be taken into consideration. (7) Proportionality is concerned with the relationship between the internationally wrongful act and the countermeasure. In some respects proportionality is linked to the 783 E. Cannizzaro, Il principio della proporzionalità nell’ordinamento internazionale (Milan, Giuffrè, 2000). 135 requirement of purpose specified in article 49: a clearly disproportionate measure may well be judged not to have been necessary to induce the responsible State to comply with its obligations but to have had a punitive aim and to fall outside the purpose of countermeasures enunciated in article 49. Proportionality is, however, a limitation even on measures which may be justified under article 49. In every case a countermeasure must be commensurate with the injury suffered, including the importance of the issue of principle involved and this has a function partly independent of the question whether the countermeasure was necessary to achieve the result of ensuring compliance. Article 52. Conditions relating to resort to countermeasures 1. Before taking countermeasures, an injured State shall: (a) call upon the responsible State, in accordance with article 43, to fulfil its obligations under Part Two; (b) notify the responsible State of any decision to take countermeasures and offer to negotiate with that State. 2. Notwithstanding paragraph 1 (b), the injured State may take such urgent countermeasures as are necessary to preserve its rights. 3. Countermeasures may not be taken, and if already taken must be suspended without undue delay if: (a) the internationally wrongful act has ceased; and (b) the dispute is pending before a court or tribunal which has the authority to make decisions binding on the parties. 4. Paragraph 3 does not apply if the responsible State fails to implement the dispute settlement procedures in good faith. Commentary (1) Article 52 lays down certain procedural conditions relating to the resort to countermeasures by the injured State. Before taking countermeasures an injured State is required to call on the responsible State in accordance with article 43 to comply with its obligations under Part Two. The injured State is also required to notify the responsible State that it intends to take countermeasures and to offer to negotiate with that State. Notwithstanding this second requirement, the injured State may take certain urgent countermeasures to preserve its rights. If the responsible State has ceased the internationally wrongful act and the dispute is before a competent court or tribunal, countermeasures may not be taken; if already taken, they must be suspended. However, this requirement does not apply if the responsible State fails to implement dispute settlement procedures in good faith. In such a case countermeasures do not have to be suspended and may be resumed.