20 the Vienna Convention, the Ruling does not appear to consider the principle that the will of the Parties must prevail and that any change made to such treaties by all of the States Parties is termed an amendment, whereas one made by agreement only among certain of the parties, is termed a modification.117 Nor does it appear to take into account that the Convention, in turn, also makes a distinction on the matter, between proposed amendments, pursuant to Article 76, 118 and drafts of additional Protocols to the Convention, in order to progressively include in its protection system other rights and freedoms regulated by Article 77. 119 Therefore, the said Protocols do not constitute a change to the Convention as such, but rather aim to add other rights not contemplated therein to the protection system that it envisages. 54. With reference to the provision of the Vienna Convention according to which “any relevant rules of international law applicable in the relations between the parties,” I should also mention that the Ruling also alludes, in a very generic manner, solely to the American Declaration of the Rights and Duties of Man.120 However, it does not point out that since the latter pre-dates the Convention, it is a resolution that was originally declarative or interpretative of a general principle of law and therefore, pursuant to Article 29(d) thereof, 121 must be considered for interpretative purposes of the Convention, but not that it interprets it. 55. Moreover, the Ruling does not comment on the protection system contemplated in the Convention, as part of the context. As mentioned previously122 this system is described in Part II of Article 39: “General rule regarding the amendment of treaties. A treaty may be amended by agreement between the parties. The rules laid down in Part II apply to such an agreement except insofar as the treaty may otherwise provide.” Article 40: “Amendment of multilateral treaties. 1. Unless the treaty otherwise provides, the amendment of multilateral treaties shall be governed by the following paragraphs. 2. Any proposal to amend a multilateral treaty as between all the parties must be notified to all the contracting States, each one of which shall have the right to take part in: a) the decision as to the action to be taken in regard to such proposal; b) the negotiation and conclusion of any agreement for the amendment of the treaty. 3. Every State entitled to become a party to the treaty shall also be entitled to become a party to the treaty as amended. 4. The amending agreement does not bind any State already a party to the treaty which does not become a party to the amending agreement; article 30, paragraph 4 (b), applies in relation to such State. 5. Any State which becomes a party to the treaty after the entry into force of the amending agreement shall, failing an expression of a different intention by that State: a) be considered as a party to the treaty as amended; and b) be considered as a party to the unamended treaty in relation to any party to the treaty not bound by the amending agreement.” Article 41: “1. Agreements to modify multilateral treaties between certain of the parties only. 1. Two or more of the parties to a multilateral treaty may conclude an agreement to modify the treaty as between themselves alone if: a) the possibility of such a modification is provided for by the treaty; or b) the modification in question is not prohibited by the treaty and: i) does not affect the enjoyment by the other parties of their rights under the treaty or the performance of their obligations; ii) does not relate to a provision, derogation from which is incompatible with the effective execution of the object and purpose of the treaty as a whole. 2. Unless in a case falling under paragraph 1 (a) the treaty otherwise provides, the parties in question shall notify the other parties of their intention to conclude the agreement and of the modification to the treaty for which it provides.” 117 118 Footnote 16 119 Idem. 120 Paras. 82 and 85 of the Ruling [Case of Cuscúl Pivaral]. 121 Footnote 50. 122 Para. 17