Invalidity of Treaties: Coercion, Error, Fraud, Jus Cogens

A treaty in force is presumed valid, and Article 42 of the Vienna Convention allows its validity to be challenged only on the grounds the Convention lists. Some grounds make a treaty voidable at the option of the injured state; others make it void from the start. This note covers each ground, the leading cases, the consequences of invalidity, and the procedure a state must follow.

1. Grounds at a Glance

Figure 1: Articles 46 to 53

• Relative grounds. Articles 46 to 50 make a treaty voidable: only the affected state may invoke them, and it can lose the right by acquiescence (Article 45)
• Absolute grounds. Articles 51 to 53 make a treaty void: they cannot be waived, and the treaty cannot be partly saved (Article 44(5))

2. Defects of Consent

• Internal law on competence, Article 46. A state may not invoke the fact that its consent was expressed in violation of its internal law on competence to conclude treaties, unless the violation was manifest, that is, objectively evident to any state acting in good faith, and concerned a rule of fundamental importance.
• Land and Maritime Boundary (Cameroon v Nigeria), 2002. Nigeria argued that the Maroua Declaration, 1975 signed by its head of state was invalid because it was never ratified by its Supreme Military Council; the Court held that a limitation on a head of state's capacity is not manifest unless properly publicised, and heads of state are presumed to have authority.
• Restriction on authority, Article 47. If a representative's authority was subject to a specific restriction, its breach may be invoked only if the restriction was notified to the other negotiating states beforehand.
• Error, Article 48. An error relating to a fact or situation assumed to exist when the treaty was concluded and forming an essential basis of consent may be invoked; not if the state contributed to the error by its own conduct or the circumstances put it on notice; an error in wording only is corrected under Article 79.
• Temple of Preah Vihear (Cambodia v Thailand), 1962. Thailand could not plead error in the map placing the temple in Cambodia, since its officials were competent to see the error and had accepted the map for decades.
• Fraud, Article 49. A state induced to conclude a treaty by the fraudulent conduct of another negotiating state may invoke the fraud; there is little practice.
• Corruption, Article 50. Corruption of a state's representative, directly or indirectly, by another negotiating state may be invoked.

3. Coercion and Jus Cogens

• Coercion of a representative, Article 51. Consent procured by acts or threats directed against the representative personally has no legal effect; the pressure on President Hácha of Czechoslovakia in 1939 is a classic example.
• Coercion of a state, Article 52. A treaty is void if its conclusion has been procured by the threat or use of force in violation of the principles of international law embodied in the UN Charter.
• Fisheries Jurisdiction (UK v Iceland), 1973. The Court accepted that a treaty concluded under the threat or use of force is void under modern international law, but found no such coercion in the 1961 exchange of notes between the UK and Iceland.
• Economic and political pressure. Proposals to include economic coercion in Article 52 failed; instead, a separate Declaration on the Prohibition of Military, Political or Economic Coercion was adopted at the Vienna conference.
• Jus cogens, Articles 53 and 64. A treaty conflicting with a peremptory norm at its conclusion is void; one that conflicts with a new peremptory norm becomes void and terminates (Topic 10)

4. Consequences

• Void treaty, Article 69. Its provisions have no legal force; each party may require the others to restore, as far as possible, the position that would have existed; acts performed in good faith before invalidity was invoked are not unlawful by reason only of the invalidity.
• Separability, Article 44. For relative grounds, the defective clauses may sometimes be separated from the rest; for coercion and jus cogens, the whole treaty falls.
• Jus cogens, Article 71. The parties must eliminate as far as possible the consequences of acts done in reliance on the void provision and bring their relations into conformity with the peremptory norm.

5. Procedure

Figure 2: Articles 65 and 66

6. Frequently Asked Questions

Can a state escape a treaty because its constitution was not followed?

Only if the violation was manifest and concerned an internal rule of fundamental importance (Article 46). In Cameroon v Nigeria (2002), Nigeria could not rely on a constitutional requirement that had not been made known to Cameroon.

Does economic pressure make a treaty void?

Not under Article 52, which covers the threat or use of force contrary to the Charter. Economic and political coercion were addressed only in a separate, non-binding declaration adopted at the Vienna conference.

7. Related Topics

• Topic 10: Jus Cogens and Obligations Erga Omnes. Peremptory norms.
• Topic 15: Law of Treaties III. Interpretation.
• Topic 17: Law of Treaties V. Termination and suspension.