The defence of ‘state of necessity’ is a ground recognised by customary international law and codified by Article 25 of the ILC’s 2001 Draft articles on Responsibility of States for Internationally Wrongful Acts. This defence has the effect of making what would otherwise have been a wrongful act become legitimate. Article 25 sets out the four principles which a state must satisfy in order to invoke ‘necessity’ as a defence – these are:451

- The act has to be the only way for the state to safeguard an essential interest against a grave and imminent peril.

- The act must not seriously impair an essential interest, of such state or states, towards which the obligation exists, or of the international community as a whole.

- The international obligation in question should not exclude the possibility of invoking necessity.

- The state should not have contributed to the situation of necessity.

- The ICJ in Gabcíkovo-Nagymaros considered the ‘state of necessity’ in relation to international watercourses.452

In this case downstream riparian Hungary halted construction of the Gabcíkovo-Nagymaros barrage system provided for in the 1977 Treaty with Slovakia, alleging that continuation would pose grave risks to the Hungarian environment and water supply. Hungary relied on the ‘state of ecological necessity’ and ‘ecological risk’ to justify this act although it acknowledged that ‘necessity’ would not preclude it from compensating upstream riparian Slovakia. The ICJ found that Hungary’s concerns were ‘an essential interest of the state’ but the potential environmental problems did not constitute a ‘grave and imminent peril’ which threatened the state’s interests.453 The court held that the acts of Hungary were not justified by the exception of necessity,454 stating that ‘such grounds for precluding wrongfulness can only be accepted on an exceptional basis’ and ‘strictly defined conditions which must be cumulatively satisfied.’455 This means that all the four principles in Article 25 of the 2001 Draft Articles must be satisfied.

450 For examination of State Necessity in International Law T Yamada ‘State of Necessity in International Law: A Study of International Judicial Cases’ (2004). Also see Tanzi and Arcari, The United Nations Convention on the Law of International Watercourses: A Framework for Sharing at 200.

451 ILC 2001 Draft Articles on Responsibility of States for Internationally Wrongful Acts, Report of the International Law Commission on the work of its 53rd session (2001) UN Doc A/56/10, at 43-365.

452 The ICJ, in the Case Concerning the Gabcíkovo-Nagymaros Project (Hungary v Slovakia) Judgement of 25 September 1997 (Gabcíkovo-Nagymaros Case) [1997] ICJ Reports 1997 7 at 36 – 45, considered the ‘state of necessity’ in relation to international watercourses – however it is important to note that the court was not asked to apply the state of necessity rule as a justification for an inequitable or significantly harmful use of a river…

453 Ibid para 53.

454 The court referred to a previous version of Article 25 of the 2001 Draft Articles which was then Article 33 of the ILC Draft Articles on State Responsibility.

455 Gabcíkovo-Nagymaros Case at 37.