Error
An error (Article 48) is a mistaken impression of facts which nullifies consensus. A State may invoke an error if it relates to a fact or situation which was assumed by that State to exist at the time when the treaty was concluded and formed an essential basis of its consent to be bound (Article 48). This provisions echos the adage "
omnis conventio intelligitur sic stantibus": A genuine consensus only exists where all essential facts were equally known by all parties. Nevertheless, a State may only invoke an error, if it has not contributed to it by his own conduct.
DeceitLike an error, fraud (Article 49) leads to a mistaken impression of reality, but unlike the former it is the consequence of a deception by the other pary or parties. The State Party victim of such an act is entitled to invoke fraud as invalidating its consent to be bound by the treaty.
The corruption of a State representative (Article 50) perverts the relationship of agency existing between this person and the State from which he has the authorization to act on its behalf. Corruption can occur either directly or indirectly, and in order to be invoked, it must be at the origin of the expression of a consent to be bound by a given treaty.
Within the boundaries set by Article 44 (4) deceived States are entitled to invalidate either the whole treaty or only parts thereof. In cases of coercion (see below) or of treaties conflicting with jus cogens, the possibility of making such a choice is not foreseen; hence, only the treaty as a whole is voidable (Artikel 44 (5)).
CoercionThe most quoted example of a coercitive measures taken against a State representative (Article 51) are the threats formulated against the Czechoslovak President Hacha in order to have him agree on the end of a independent Czechoslovakia.
"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
Charter of the United Nations." (Article 52). Such a coercion is indeed prohibited by Article 2 (4) of the
Charter of the United Nations. Since consensus for the inclusion of a definition of "threat" in the
Vienna Convention itself was lacking, the United Nations Conference on the Law of Treaties adopted at together with the
Vienna
Convention a "
Declaration on the Prohibition of Military, Political or Economic Coercion in the Conclusion of Treaties". Paragraph one of this legally non-binding declaration "
solemnly condems the threat or use of pressure in any form, whether military, political, or economic, by any State in order to coerce another State to perform any act relating to the conclusion of a treaty in violation of the principles of the sovereign equality of States and freedom of consent".
However, in the context of diplomatic protection the question of the legitmacy of the use of force is disputed. Therefore, for some there is no defect in the consent of a State which has been brought about under such circumstances. As a matter of course, such an argumentation is very dangerous, since it furthers aggressive behaviour shown under the pretext that is is legitimated by the international law of diplomatic protection. But how are peace treaties to be judged in the light of Article 52, since most of them are the result of armed
conflicts ?
