18. That said, the principal rule for the interpretation of treaties contained in the Vienna
Convention on the Law of Treaties,31 is that:
“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.”
19. This rule includes four means of interpretation.32 One is the method based on good
faith, which means that what was agreed by the States Parties to the treaty concerned
should be understood based on what they effectively had the intention of agreeing to
so that it is truly applied and has practical effects. In this regard, good faith is closely
related to the “pacta sunt servanda” principle.33 The second, is the textual or literal
method, which refers to the analysis of the text of the treaty, the wording used, and
the ordinary meaning of its terms. The third is the subjective method that seeks to
establish the intention of the States Parties to the treaty by analyzing the travaux
préparatoires and the subsequent conduct of the States Parties with regard to the
treaty. And the forth is the functional or teleological method that seeks to determine
the object and purpose of the treaty. Since these four means of interpretation are
included in the same phrase, forming a single rule, they should be applied
simultaneously and harmoniously, without preferring or downplaying one or the other.
This is the main characteristic that distinguishes the interpretation of treaties from that
of other norms.34
20. Regarding the special rule established in Article 29 of the Convention,35 known as the
pro personae principle, it should be recalled that this is a rule relating to the
31
32
Hereinafter, the Vienna Convention.
Art. 31 of the Vienna Convention: “General rule of interpretation.
“1. 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.”
2. “The context for the purpose of the interpretation of a treaty shall comprise, in addition to the
text, including its preamble and annexes:
(a) any agreement relating to the treaty which was made between all the parties in connection with
the conclusion of the treaty;
(b) any instrument which was made by one or more parties in connection with the conclusion of the
treaty and accepted by the other parties as an instrument related to the treaty.
3. There shall be taken into account, together with the context:
(a) any subsequent agreement between the parties regarding the interpretation of the treaty or the
application of its provisions;
(b) any subsequent practice in the application of the treaty which establishes the agreement of the
parties regarding its interpretation;
c) any relevant rules of international law applicable in the relations between the parties.”
4. A special meaning shall be given to a term if it is established that the parties so intended.”
33
Supra, footnote 15.
34
As in the case of article 19 of the Civil Code of Chile: “When the meaning of the law is clear, its literal meaning should not be
ignored, on the pretext of consulting its spirit. However, to interpret an obscure expression of the law, it is possible to have recourse
to its intention or spirit, clearly apparent in it, or to the reliable history of its creation.”
35
“Restrictions Regarding Interpretation. No provision of this Convention shall be interpreted as:
(a) permitting any State Party, group, or person to suppress the enjoyment or exercise of the rights and freedoms recognized in this
Convention or to restrict them to a greater extent than is provided for herein;
(b) restricting the enjoyment or exercise of any right or freedom recognized by virtue of the laws of any State Party or by virtue of
another convention to which one of the said states is a party;