Orginally, the international treaty rules were either part of customary international law or belonged to the general principles of law; today the rules governing international treaties which are concluded between States in written form are codified. The codification governing this legal area is the Vienna Convention on the Law of Treaties (Vienna Convention) of 1969 which has entered into force on 27 January 1980. Although the Vienna Convention is not applicable to treaties concluded before its entry into force (Article 4) it is de facto applied to those too, since it incorporates - at least to a large extent - customary rules which were already applicable before this date. Moreover, the Vienna Convention applies only in the absence of other applicable agreements and is therefore of subsidiary character.
A Vienna Convention on the Law of Treaties between States and International Organizations or between International Organizations dating from 1986 has reproduced the provisions of the Vienna Convention. It reflects to a large extent international customary law, too; however, it has not yet entered into force.
Finally, a Vienna Convention on Succession of States in respect of Treaties, concluded in 1978, entered into force in 1996, but since it has been ratified by 15 States only, it cannot be considered as a source of universal international law. Furthermore, it has hardly had any impact on state practice, the noteworthy exception being that practice widely follows the rule according to which a successor State can establish its status as party of a multilateral treaty to which its predecessor State already belonged through a declaration of succession.
Generally speaking, one can say that customary international law is rather blurred in this regard.
Basically, two types of treaties are two be distinguished:
- bilateral treaties which are concluded between two States only
and
- multilateral treaties concluded between at least three States;
the treaties which have attracted the largest numbers of
parties are called universal.
Amongst multilateral treaties, one can distinguish between "open" and "restricted" treaties. Whereas every State can become a party to the "open" ones, access to the latter category of treaties is excluded for those States which do not belong to the original States Parties, unless an agreement to the contrary has been entered into.
Hence, every State can accede to the Vienna Convention (open treaty), but only the signatory States of the Convention on the Regulation of the Navigation on the Danube River from 1948 could originally ratify this (restricted) treaty: hence the accessions of Austria and Germany had to be approved by the original States Parties in 1960 and 1999, respectively, by way of supplementary agreements with these two countries.
The Vienna Convention which consists of 85 articles, eight parts and an annex includes and materializes five fundamental legal principles.
Free consent and good faith (bona fide in Latin) are the leading principles which ought to be always followed by States in the course of their relations with one another.
The other major principles which also emanate from the Roman Law tradition apply in particular
- either to the conclusion of treaties:
- pacta sunt servanda (a treaty is binding upon the parties)
- or to the interpretation or application of treaties:
- omnia conventio intelligitur rebus sic stantibus
(viz. the clausula rebus sic stantibus according to which a
fundamental change of circumstances jeopardizes the validity
of treaties)
- favor contractus (it is better to seek the maintenance rather
than the termination of a treaty)
These five principles will be subject to closer scrutiny on this website and the application of the two major principles (free consent and good faith) will be the object of a separate chapter. Of course, the delimitation between these principles can be vague, but eventually they are mutually supportive of each other.
-
Free consent
Good Faith
Pacta sunt servanda
Clausula rebus sic stantibus
- Favor contractus
