The interpretation of treaties is one of the very important and practical topics in international law, and the rules regarding treaty interpretation are provided in Articles 31 to 33 of the 1969 Vienna Convention. Article 31 addresses the general rule of interpretation, while Article 32 outlines supplementary means of interpretation. Sometimes, the general rule of interpretation may not be sufficient for interpreting a treaty or may yield an uncertain result; therefore, it is necessary for the interpreter to refer to supplementary means of interpretation. Many questions still arise regarding these supplementary means; thus, this research aims to examine and analyze the role of supplementary means of interpretation in the process of treaty interpretation based on the rules of the 1969 Vienna Convention and international judicial practice. The research concludes that international judicial practice regarding the use of supplementary means of interpretation to confirm the meaning derived from the application of the general rule of interpretation has not been uniform. On the other hand, it can be said that the majority of the interpretative provisions of the Vienna Convention essentially codify the practice of the International Court of Justice.

Abstract Undoubtedly, international treaties are one of the most important sources of international law and have a special place in international law due to their stability, clarity, and precision in proving and explaining the obligations of the parties. However, it can be said that despite the great care and attention taken by negotiators when drafting treaty provisions, there is no treaty that does not raise some issues regarding treaty interpretation, especially as each state tries to interpret the treaty in accordance with its national interests. According to Article 31(1) of the Convention on the Law of Treaties, a treaty must be interpreted in accordance with the ordinary meaning given to the terms of the treaty in their context and having regard to the subject matter and purpose of the treaty.Therefore, in many cases, it is sufficient to consider the ordinary meaning of treaty terms in their context and with regard to the subject matter and purpose for interpreting treaty provisions and terms .However, in some cases, the text of the treaty may not be sufficient to interpret the terms of the treaty, and the interpreter needs to refer to other rules outside the text of the treaty being interpreted (including customary international law) in order to properly carry out the interpretation process. The relationship between the treaty and other relevant rules of international law, including customary international law, is of particular importance. In this context, the relevant rules of international law can affect the treaty in various aspects; one of these important aspects is its effect on the interpretation of the treaty. Therefore, the purpose of this article is to explain the role of customary international law in the interpretation of treaties. In this paper, by using library sources, international documents, and international judicial decisions and through a descriptive-analytical method, the position of the rules of customary international law in the interpretation of treaties will be studied. Article 31(3)(c) of the 1969 Vienna Convention on the Law of Treaties states that in the interpretation of a treaty, together with the context, “any relevant rules of international law applicable in the relations between the parties” shall be taken into account. Therefore, in interpreting a treaty, in addition to its text and context and other elements of the general rule of interpretation contained in Article 31 of the Convention on the Law of Treaties, the rules of customary international law must also be taken into account. It seems that the importance of Article 31(3)(c) of the Convention on the Law of Treaties stems from the fact that it refers to the relationship between the provisions of the treaty and other relevant rules of international law. Therefore, Article 31(3)(c) is related to the issue of “systemic integration” in the international legal system. The principle of systemic integration means that treaties must be interpreted and implemented within the framework of international law and that the spirit of the rules of international law must always govern them. It is worth noting that, according to the general rule of interpretation provided for in Article 31 of the Vienna Convention, the text of the treaty is the starting point of the interpretation process. However, relevant rules of international law, including customary international law, must be considered in context. Hence, the rules of customary international law play an auxiliary or secondary role in the interpretation of treaties. In other words, the treaty being interpreted retains the primary role in the interpretation process. On the other hand, it seems that in the process of interpreting a treaty, the interpreter must consider the customary rule applicable in the relations between the parties. This means that an interpretative authority does not have the right to exercise discretion but must consider customary law. According to Article 31(3)(c) of the Convention on the Law of Treaties, in order to take into account, the rules of customary international law in the process of interpreting a treaty, the customary rules must both be relevant to the treaty under interpretation and applicable in the relations between the parties to the treaty under interpretation. Therefore, it can be said that customary rules can include general, regional, or local custom. The use of customary international law rules in the process of interpreting treaties is of particular importance because it can clarify the ambiguous meaning of treaty terms or determine the scope of treaty provisions. Furthermore, taking into account the rules of customary international law in the treaty interpretation process helps to prevent the interpretation and application of a treaty as an independent regime. Therefore, it reduces the fragmentation of international law and promotes systemic integration in the international legal system. International jurisprudence has played an important role in explaining the position of customary international law rules in the interpretation of treaties. International judicial authorities have referred to the rules of customary international law applicable to the relations between the parties, especially when the terms used in the treaty are ambiguous or have a well-known meaning in customary international law, or to take into account the principle of systemic integration.

The interpretation of treaties has important, wide-spread and explicated affects in international law. The awards of Iran-US Claims Tribunal, with more than a quarter of century in operation since 1982 have profoundly affected the different fields of international law, including the interpretation of treaties. The present article deals with the Tribunal's practice in the subject of interpretation of treaties. The Tribunal's interpretation of Algerian Declarations and other international agreements, in addition to creating good and reliable precedents, have some effects on the development of international law in the subject of interpretation of treaties. The Tribunal always applies the 1969 Vienna Convention of the Law of Treaties, in particular Articles 31 and 32, and has interpreted Algerian Declarations in conformity with the above provisions. One of the principles and rules invoked by the Tribunal is the principle of prevailing concept under which each word must be interpreted in its own context and with regard to the object and purpose of a treaty.

Purpose: The science of interpretation, as the most important science responsible for understanding the Qur'an, needs to be methodized and updated so that the teachings of the Qur'an can be used easily for all classes of people. In the present study, the meaning of "future research in interpretation" is the ability to create desirable models for more efficient interpretation in the future, by using scientific tools, creativity and relying on the foundations and rules of interpretation and compensating the damages of interpretation in the past.Method: This research, with descriptive analytical method, answers the question, what are the fields and requirements of future research in interpretation? Findings: The results of the current research are based on the fact that special attention to the Qur'an, as the most important source of interpretation, rationality and methodical consideration in interpretation, attention to the prerequisites of interpretation, interpretation based on the requirements of the time, the need to pay attention to thematic interpretation, studying on the history of interpretation and observing the manners and conditions of interpretation are one of the most important requirements of interpretation in the future. Results: Considering the developments that will take place in the field of knowledge, methods and expectations from science in the future, the interpretation will also change. For this reason, in order not to cause various damages to the interpretation of the Qur'an, it is necessary to pay attention to the various contexts, principles and requirements of the interpretation of the Qur'anic commentators and scholars.

Article 31(3)(c) of the 1969 Vienna Convention stipulates that in the interpretation of a treaty, together with the context, “any relevant rules of international law applicable in the relations between the parties” shall be taken into account. Therefore, in treaty interpretation, in addition to its text and context and other elements of the general rule of interpretation set out in Article 31 of the Vienna Convention, the relevant rules of international law should also be considered. The main question this research intends to answer is: What is the position of relevant rules of international law in the interpretation of treaties? It appears that a treaty should be interpreted in harmony with other relevant rules of the international legal system of which it forms part. Thus, employing the relevant rules of international law in the interpretation of a treaty can guarantee the unity and systemic integration of the international legal system. This research will study the position of relevant rules of international law in the interpretation of treaties by analyzing international documents and jurisprudence.

According to common Articles 31 and 32 of the 1969 Vienna Convention on the Law of Treaties and the 1986 Vienna Convention on the Law of Treaties between States and International Organizations, subsequent practice of the parties to a treaty is an authentic element in the interpretation of that treaty,whether it is a mere interstate treaty or a constituent treaty of an international organization. Because of the growth and development in the life of an IO and originating from its subsequent practice, the constituent treaty of that organization entails a modern reading. Directing an IO in a legal and desirable way is based on Constituent treaty of that organization. To the same extent, this role can and should be expected from the organization's own subsequent practice. Legal precedent, ILC findings and legal doctrine confirm this effect. Examination the role of subsequent practice by IO's organs and practice followed by the parties of the constituent treaties of international organizations in the interpretation of that treaty, is this paper's purpose.

Nowadays there are many aliens’ populations living in other countries. Forced Migration and Study of Religious Sciences are two main reasons introducing Iran as a host country. This paper Intends to clarify some questions about enforcement of Iranian civil code which determines the applicable law on the personal status of foreigners. There are some disagreements about the law governing personal status and situation of foreigners and it is because of some ambiguities in the Civil Code. There are two main interpretations about the Civil Code: the first view claims that the law of Iran must principally apply to Personal status of foreigners unless there is a treaty between Iran and the foreigner’ s national state which resolve the problem; but the second view defends applying law of the foreigner’ s national state and believes that absence of a treaty has no effect. According to the historical events and legal facts with an analytical view, this paper proves that the second interpretation is more efficient and rational.

Providing the legal systems with stability and dynamism requires the existence of stable rules and at the same time with a necessary degree of flexibility to ensure that the legal system would be practical and effective if important and real changes occur in social situations. International judicial authorities, in the course of litigation, identify the basis and reality of the rules and legal principle through interpretation and adaptation with the subject matter of the cases, and in this way, meet the needs arising from developments in the international situation. The European Court of Human Rights, whose main function is to resolve disputes arising from the European Convention on Human Rights, in some cases, through the use of a static interpretation, against dynamic interpretations, has insisted on the provisions of the Convention and, in some cases, having due regard to the structure of the European community, used the evolutionary and dynamic interpretation of the provisions of the Convention. The Court, in many cases, referred to a concept called “ the European Consensus” to justify implementing the dynamic interpretation of the Convention and responded to the new situations. This approach has been faced with various agreements and disagreements. The European Court of Human Rights by applying the dynamic interpretation method takes into account the will of States as a key element in the evolution of rules and obligations in international law and at the same time has undermined the need for expressing State’ s will to accept these developments. In this way, the human rights rules and obligations enshrined in the Convention are evolving with changes in the requirements of the present time and social realities.

In the course of international tribunals’ adjudications, one of the most important issues to deal with is to solve the problem of conflict of laws through determining the applicable law. Monism and the priority of international law over domestic law was accepted and confirmed by the majority of jurists, especially those believe in monism doctrine, from different legal systems. For the lawyers and arbitrators the interpretation of treaties and contracts is a vital and basic step in litigation or arbitration procedure. Toward determining of rights and duties of parties in investment law, the occurrence of conflict of laws between international law and domestic law is a usual and ordinary subject matter. Notwithstanding the indications of doctrine of priority of domestic law over international law, but the search in the Treaties, Contracts, Doctrine and Legal precedents verify the contrary view point. Today the states liabilities in investment arbitration even with the contractual origination, changed to the states international liabilities, with presence of new provisions like as umbrella clause (As catch all provision), which reaffirm on the priority and influence of international law over domestic law. My uppermost aim in writing this article has been to study and show this evolutionary legal transformation in international investment law and to meet that end legal precedent has been examined.

Arguing that human rights treaties by their nature are different from other international agreements, this Article deals mainly with such questions as succession of states in respect of human rights treaties and reservations to such instruments.  In contrast to other treaties, which are generally “inter-states exchange of interests”, human rights documents are protective instruments according to which states parties undertake to restrain their discretion as regards fundamental rights and freedoms both internally and internationally. This is why adopting different approach to offer a proper theoretical framework as to the above questions seems to be necessary. In addition to author’s classification of human rights treaties into six categories, the idea of automatic succession of states to human rights instruments and invalidity of certain reservations to these treaties are main contribution of this study.