"
A treaty shall be interpreted in good faith in accordance with the
ordinary meaning to be given to the terms of the treaty in their context
and in the light of its object and purpose." (Article 31 (1); here again, as in the Articles 18, 19, 20 (2), 41 (1)(b)(ii) and 58 (1)(b)(ii), we find again the vague concept of "object and purpose of a treaty").
The context includes, in addition to the treaty text itself, the preamble and the annexes as well as other agreements and documents which are considered by the parties as being instruments related to the treaty (Article 31 (2)). Furthermore, any subsequent practice in the application of the treaty which establishes the agreement of the parties regarding its interpretation has to be taken into account, too.
According to the "Appellate Body", the highest dispute settlement organ of the
World Trade Organization (WTO), the context of a legal instrument is also constituted by the other treaties its parties adhere to. Hence, in the case concerning "
Standards for Reformulated and Conventional Gasoline" the Appellate Body explained that the
Marrakesh Agreement Establishing the World Trade Organization (the "WTO Agreement") "is not to be read in clinical isolation from public international law". That means, in particular, that the trade provisions of the
WTO Agreement have also to be interpreted in the light of
conventions for the protection of the environment, provided that they are in force between the States Parties of the
WTO Agreement.
Finally, there are supplementary means of interpretation as, for instance, the preparatory work of the treaty (so called "travaux préparatoires") and the circumstances of its conclusion (Article 32).
A specificity of international conventions lies in the fact that they are authenticated in several languages (see Article 33). With regard to treaties concluded under the auspices of the United Nations, these languages are regulary: Arabic, Chinese, English, French, Spanish and Russian.
The terms of the treaty are presumed to have the same meaning in each authentic text (Article 33 (3)). In the case of several Protocols to the Convention for the Protection of the Alps (the Alpine Convention) there were so many difrences in the texts authenticated in French, German, Italian and Slovene that a separate conference had to be convened for the purpose of their harmonization (see Article 79 (3)).
The
LaGrand case revealed a divergence between the equally authentic English and Fench versions of
Article 41 of the Statute of the International Court of Justice. Hence, the
Court had to examine the object and purpose of the Statute together with the context of
Article 41. In this way, the Court, in its judgement of 27 June 2001, "
reached the conclusion that orders on provisional measures under Article 41
have binding effect".
