b) Termination of treaties as a consequence of a defect of consent

Every person invested with appropriate full powers has the authority to express the consent of the State which he represents to be bound by a given treaty. If this authority has been made subject to a specific restriction which has then not been observed by the representative, the State may invoke this fact as invalidating its consent. However, this possibility only exists, if the restriction had been notified to the other negotiating States before the expression of consent (Article 47), because if this prior notification did not take place, it would be easy to invoke defect of consent by mere political opportunism which, in return, would constitute a behaviour contrary to the principle of good faith.

The other defects of consent are enumerated exhaustively in the Articles 48 to 52 of the Vienna Convention. They are the consequence of

- an error (Article 48)

- deceit (Articles 49 and 50)

- or coercion (Articles 51 and 52).

Defects Of Consent

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.

Deceit
Like 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)).

Coercion

The 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 ?

c) No derogation of jus cogens

With the exception of the provision contained in Article 22, para.1 which emanates from the favor contractus principle, only peremptory norms of general international law (Latin: jus cogens) can stand in the way of an agreement which has been freely entered into. Indeed, Article 53 of the Vienna Convention specifies that a treaty conflicting with jus cogens at the time of its conclusion is void. Similarly, a treaty becomes void and terminates, if it is in contradiction with a peremptory norm of international law which has newly emerged (jus cogens superveniens - Article 64)

In that context we are in the presence of quite obscure provisions despite the definition of jus cogens contained in Article 53: According to it, 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.

As the International Law Commission (ILC) nevertheless remarked itself in 1969 in its commentary on the draft articles for the international law of the treaties, there is no simple criterion which would allow to determine whether a rule belongs to jus cogens.

This state of affairs has hardly evolved, although it seems that certain international norms for which criminals will have to stand before the International Criminal Court after having breached them constitute to a large extent the body of these sought jus cogens rules. These penal provisions concern the prohibition of genocide, war crimes, crimes against humanity and the crime of aggression.

Eventually, jus cogens seems to be a concept invented by international law experts who had been pursuing the aim of allowing natural law ideas to erupt into the legal regime of international treaties.