¹ Opened for signature May 23, 1969, 1155 UNTS 331.

² Costa Rica v. Nicaragua (Central Am. Ct. Justice Sept. 30, 1916), 11 AJIL 181 (1917); El Salvador v. Nicaragua (Central Am. Ct. Justice Mar. 9, 1917), id. at 674.

³ Costa Rica v. Nicaragua, 11 AJIL at 210, 227–29; El Salvador v. Nicaragua id. at 729.

⁴ Article 4 of the Vienna Convention, supra note 1, provides in part: “the Convention applies only to treaties which are concluded by States after the entry into force of the present Convention with regard to such States.”

⁵ Article 53 provides:

A treaty is void if, at the time of its conclusion, it conflicts with a peremptory norm of general international law. For purposes of the present Convention, a peremptory norm of general international law is a norm accepted and recognized by the international community of States as a whole as a norm from which no derogation is permitted and which can be modified only by a subsequent norm of general international law having the same character.

Id. Such principles may include prohibitions of the use or threat of force, genocide, slavery, gross violations of the right of peoples to self-determination and racial discrimination. See A. Cassese, International Law in a Divided World 179 (1986).