1 Vice-President Weeramantry and Judges Bedjaoui and Koroma appended separate opinions. Judges Oda, Ranjeva, Herczegh, Fleischhauer, Vereshchetin and Parra-Aranguren and Judge ad hoc Skubiszewski appended dissenting opinions. President Schwebel and Judge Rezek appended brief declarations explaining their votes. A first round of public hearings was held in the Peace Palace in The Hague on March 3–7 and March 24–27, 1997, after which the ICJ judges made a visit in situ under Article 66 of the Rules of Court to obtain evidence at the place to which the case relates (April 1–4, 1997). This was the first site visit in the history of the ICJ. See 1997 ICJ REP. 3 (Order of Feb. 5). A second round of oral proceedings took place on April 10, 11, 14 and 15, 1997. See Judgment, paras. 10–11 [hereinafter slip op.].

2 Slip op., para. 46. The Court thus adopted the cautious attitude that Hungary had requested it to take in this respect. See id., para. 42.

3 Id., paras. 28, 48.

4 The Court disagreed with Slovakia that ecological necessity/risk could not constitute a circumstance precluding wrongfulness of an act, but wrongfulness could be precluded only if the strictly defined criteria laid down in ILC draft Article 33 (reflecting customary law) were cumulatively satisfied. Slip op., paras. 44, 51. See also Report of the International Law Commission on the work of its thirty-second session, [1980] 2 Y.B. Int’l L. Comm’n 34, UN Doc. A/CN.4/SER.A/1980/Add.1 (Part 2).

5 Hungary argued that the building of the Nagymaros dam would cause the bed of the Danube to silt up, negatively affecting the quality of the water collected in the bank-filtered wells. Slip op., para. 40.

6 Id., paras. 99–100. The 1969 Vienna Convention is not directly applicable to the 1977 Treaty because both parties ratified the Convention only after the conclusion of the 1977 Treaty. For the Convention, opened for signature May 23, 1969, see 1155 UNTS 331 (entered into force Jan. 27, 1980).

7 The Court agreed with Slovakia that a state of necessity is not a ground for the termination of a treaty; it may be invoked only to relieve a state of responsibility for failure to implement a treaty. Slip op., para. 101.

8 Hungary relied on Article 61 of the Vienna Convention, supra note 6. That provision requires the “permanent disappearance or destruction of an object indispensable for the execution” of a treaty. However, the Court noted that the Treaty provides means for any required readjustments. Slip op., paras. 102–03.

9 Hungary relied on Article 62 of the Vienna Convention, supra note 6, and cited profound political changes, the project’s diminishing economic viability, the progress of environmental knowledge and the development of new norms and prescriptions of international environmental law. However, the Court considered that these events could not be said to have been completely unforeseen in 1977; nor did the existence of the stated circumstances at the time of the Treaty’s conclusion constitute an essential basis of the consent of the parties to be bound by the Treaty. Slip op., para. 104.

10 Hungary relied on Article 60 of the Vienna Convention, supra note 6. However, in the Court’s view, Czechoslovakia’s material breach of the Treaty (the actual putting into operation of Variant C) did not occur until October 1992, making the notification of termination by Hungary on May 19, 1992, premature. Besides, Hungary, by its own conduct, had prejudiced its right to terminate the Treaty. Slip op., paras. 105–10.

11 Hungary argued that the previously existing obligation not to cause substantive damage to the territory of another state had evolved into an erga omnes obligation of prevention of damage pursuant to the “precautionary principle.” The Court considered that it was not required to examine the scope of Article 64 of the Vienna Convention on the Law of Treaties, supra note 6, given that neither Hungary nor Slovakia contended that new peremptory norms of environmental law had emerged since the conclusion of the 1977 Treaty. Slip op., paras. 97, 112.

12 Slip op., para. 112. According to Article 1, paragraph 4 of the Treaty, the Joint Contractual Plan (JCP), as an instrument complementing the Treaty, was to set forth the technical specifications and operating and maintenance rules for the system of works in conformity with which the joint investment was to be carried out. Apparently, the complete text of the JCP was never submitted to the Court.

13 Id., paras. 114–15. See Vienna Convention on the Law of Treaties, supra note 6, Art. 26.

14 “[I]n so far as [Czechoslovakia] then confined itself to undertaking works which did not predetermine the final decision to be taken by it.” Slip op., para. 88.

15 Id., para. 75 (citing Admissibility of Hearings of Petitioners by the Committee on South West Africa, 1956 ICJ Rep. 23, 46 (Advisory Opinion of June 1) (Lauterpacht, J., sep. op.)).

16 Id, paras. 77 and 85.

7 This is reflected in Article 12 of the 1978 Vienna Convention on Succession of States in Respect of Treaties, opened for signature Aug. 23, 1978, 17 ILM 1488 (1978), which according to the Court reflects a rule of customary international law. Slip op., para. 123.

18 Slip op., para. 133. Hungary argued that future relations between the parties, as far as Variant C is concerned, are not governed by the 1977 Treaty. Id., para. 125.

19 Id., paras. 134–36.

20 Id., para. 150.

21 Through the dissents we learn that there was disagreement among the judges on whether to separate the operative paragraph that deals with the compensation issue into two paragraphs so that it could be voted on as two separate issues. Apparently, the majority was in favor of a single vote, prompting several judges to dissent where they otherwise agreed, at least in part, with the operative paragraph concerned. See Dissenting Opinions of Oda, J. (para. 2), Vereshchetin, J. (final para.), and Parra-Aranguren, J. (para. 21).

22 Slip op., para. 154.