Grounds of invalidity

There were no rules placing restrictions on the freedom of States as to the object of treaties. States were therefore allowed to regulate their own interests as they thought best, and even to agree on offences or attacks on other States or on the partition of their territory. The only grounds of invalidity were minor ones: (i) using force or intimidation against the State official making the treaty; (ii) inducing the other party through misrepresentation to enter into an agreement (for example, the conclusion of a boundary treaty based on a map fraudulently altered by one of the parties); (iii) the insertion of errors a s to facts (for example, an incorrect map, in the case of a boundary treaty). In addition, (a) all of these grounds of invalidity were on the same legal footing: they could all make a treaty voidable if the party against which the grounds of invalidity had been invoked was willing to consider the treaty null and void, or a dispute resolution mechanism made it possible for the parties to reach agreement; (b) only the party to a treaty allegedly damaged by the treaty's invalidity was legally entitled to claim that the treaty was not valid; the other parties (in the case of a multilateral treaty) had no say in the matter.

Under the Vienna Convention a major cause of injustice in the making of treaties - coercion exercised by a powerful State against another State - has been regarded as making the treaty null and void. Article 52 of the Convention covers coercion by the threat or use of military force contrary to the UN Charter, while a Declaration adopted by the Vienna Diplomatic Conference calls upon States to refrain from economic and political coercion as well.

What is very novel, and marks a momentous advance in the field of the law of treaties, is the distinction drawn in the Convention between 'absolute and 'relative' grounds of invalidity. The former (coercion against a State representative; coercion against the State as a whole; incompatibility with jus cogens; on this notion implies that: (1) any State party to the treaty (that is, not merely the State which has suffered from possible coercion or which might be prejudiced by actions contrary to a peremptory rule) can invoke the invalidity of the treaty; (2) a treaty cannot be divided into valid and invalid clauses, but stands or falls as a whole (Article 44.5); and (3) possible acquiescence does not render the treaty valid (Article 45). If one of these grounds is established, the treaty is null and void ex tunc that is since the moment it was concluded.

In contrast, grounds of relative invalidity are: error, fraud, corruption, manifest violation of internal law or of the restrictions of the powers of the State representative who has concluded the treaty. These grounds may only be invoked by the State that has been victim of error, fraud, corruption or whose representative has acted in manifest breach of internal law or of the restrictions on his powers.