Agreement” is binding for Battenland and Alamaguay
According to Vienna Convention on the Law of Treaties he pacta sunt servanda rule is universally recognized principle. It means that every treaty in force is binding upon the parties to it and must be performed by them in good faith.
As the "1925 Agreement” was ratified and entered into force on 1 December 1925, it is binding to the contesting parties.
Agreement” regulates the status of the Oxbow Marsh
According to Article 1 of the “1925 Agreement”:
The course of the Varsho River shall constitute the permanent and inviolable boundary between the Royal Kingdom of Battenland and the Republic of Alamaguay, from the place where the Varsho leaves the Harahkaraiac territory to where it enters the Sea of Dinghun.
The Article 2 states:
Battenland shall possess henceforth in complete sovereignty the country, lands and domains situated on the right bank of the Varsho, and Alamaguay shall possess henceforth in complete sovereignty the country, lands and domains on its left bank, both as the Varsho lies north and south of the Great Lake Kilgus.
These provisions explicitly recognize that the Oxbow Marsh is a part of the sovereign territory of the Kingdom of Battenland, as it is situated on the right bank of the Varsho.
In order to interpret these provisions we would like to refer to Vienna Convention on the Law of Treaties. As the ICSID Tribunal specified in the Phoenix Award, ‘it is not disputed that the interpretation of the ICSID Convention and of the BIT is governed by international law, including the customary principles of interpretation embodied in the Vienna Convention on the Law of Treaties and the general principles of international law.’ The International Court of Justice reiterated in the Costa Rica v. Nicaragua case the articles 31 and 32 reflected customary international law, and “neither the circumstance that Nicaragua is not a party to the Vienna Convention on the Law of Treaties nor the fact that the treaty which is to be interpreted here considerably predates the drafting of the said Convention has the effect of preventing the Court from referring to the principles of interpretation set forth in articles 31 and 32 of the Vienna Convention.”
According to Vienna Convention 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. So, this provision refers to literal (ordinary meaning of the terms), systematic (context of a treaty) and teleological (in the light of object and purpose) methods of interpretation. Interpretation under article 31 focuses on a treaty's ordinary meaning which is deemed to express the intentions of the parties. The meaning must be consistent with the object and purpose of the treaty and its related documents.
A term can have a special meaning only if its proponent can show that the term should have that special meaning.
In the 1948 advisory opinion Conditions of Admission of a State to Membership in the United Nations (Conditions of Admission), the ICJ did not resort to travaux preparatoires because it found that the text of article 4( 1) of the Charter of the United Nations (U. N. Charter) was sufficiently clear. The court found that the conditions were exhaustive because the natural meaning of the text clearly demonstrated the intentions of the parties. Only a compelling reason would have justified looking beyond the natural meaning of the words. The court followed the practice of the Permanent Court of International Justice (PCIJ) in not resorting to travaux preparatoires where the text of the convention is “sufficiently clear in itself.” Thus, the method of interpretation in this case was consistent with the textualist approach.
The article 1 of “1925 Agreement” uses the words ‘permanent’ and ‘inviolable’which are related to word ‘boundary’.And the word “boundary” is connected to the course of Varsho River.
As it was admitted above the term can have a special meaning only if its proponent can show that the term should have that special meaning. At first, neither Battland nor Alamaguay anticipated in concluded “1925 Agreement” that such term as “boundary” is determined as “permanent” and “inviolable” in the exact time and even when a course of river is permanent, but absence the provision which predict effects of the change in the course of the river, lack of the domestic legislation and no regulation in international law means that Parties expressly established in “1925 Agreement” that the course of the river should be the boundary and can not be changed. As follow from this point if the course of river changed in any way it should leaves the boundary. Secondly, in the “1925 Agreement” term “boundary” connected to the course of river Varsho. It fairly means that Paties determines the course of river Varsho as boundary not the line on land on which river flew past.