a) The expression of free consent
the Vienna Convention which governs agreements concluded in written form between States, confirms in its Article 6 that every State possesses capacity to conclude treaties. The will of a State finds its expression through persons who are authorized to do so or who are considered to be state representatives.
Since international treaty law in its entirety is subject to the free consent principle. it is quite logical that the Vienna Convention offers a broad choice of possibilities to express consent (Article 11), i.e.
- - signature,
- exchange of instruments constituting a treaty - - (in the case of bilateral treaties this often happens through the
- - exchange of notes),
- - ratification,
- - acceptance,
- - approval,
- - accession or
- - by any other means if so agreed.
A typical clause of entry into force can be found in Article 84 of the Vienna Convention itself which reads:
"1. The present Convention shall enter into force on the thirtieth day following the date of deposit of the thirty-fifth instrument of ratification or accession.
2. For each State ratifying or acceding to the Convention after the deposit of the thirty-fifth instrument of ratification or accession, the Convention shall enter into force on the thirtieth day after deposit by such State of its instrument of ratification or accession."
The States Parties - primarily the contracting States (see Article 2 (1)(f)) - can also agree to apply a treaty provisionally pending its entry into force (Article 25). This agreement can be laid down in the treaty itself or in another way. If this done in the treaty itself, the agreement enters into force with its signature (and which in this case remains, of course, subject to ratification).
For reasons to be found in their own domestic legislation it is not possible for some States -
Finally, it should be mentioned that there are constitutions like that of Portugal (see Artikel 8) which do not authorize States to express their consent through all of the means enumerated in Article 11 of the Vienna Convention; hence, for Portugal there is only a possibility to ratify or approve a treaty. Since this is the result of a domestic provision, a consent which would be expressed in a different manner would not be flawed from point of view of international treaty law, because the ways and means to express consent are already determined by customary international law and not only by the Vienna Convention to which, by the way, Portugal is not a party.
with regard to the conclusion of treaties
b) Pacta tertiis nec nocent nec prosunt
A treaty binds the parties and only the parties; it does not create obligations for a third State without its consent (Article 34), since sovereignty implies that there is no agreement without free consent. "
The acceptance of an obligation by a third State must be expressed both expressly and in writing (Article 35), in order to avoid doubts as to the extent of the obligation which had been previously defined by others.
A consent which as been expressed in such a way can be qualfied as quasi-contractual. Hence, it is only logical that the obligation can only be revoked or modified with the consent of all parties to the treaty as well as of the third State, unless it is established that they had otherwise agreed (Article 37(1)).
Although a third State cannot be granted a right without its approval, its assent is nevertheless presumed (Article 36(1)). A third State which exercising such a right is under an obligation to comply with the conditions for its exercise provided for in the treaty or established in conformity with the treaty (Article 36(2)). The rights granted to a third State can be revoked by the States Parties unless it is established that the right was intended not to be revocable or subject to modification without the consent of the third State. In such a case, the burden of proof lies with the third party benefiting from the right or rights.
The principle according to which a treaty cannot create rights or obligations for a third party without its consent is expressed in Latin by the phrase "pacta tertiis nec nocent nec prosunt". This rule also applies when two or more parties of a multilateral convention conclude an agreement to modify the convention only in relation to each other, since they hereby exclude third States from their agreement in spite of the fact that the latter are parties to the original treaty (see Article 41).
