Treaty Interpretation in International Law

Elaboration, 2001

6 Pages

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Principles of Treaty Interpretation in International Law

(a) The purpose of interpreting texts of legal significance is to establish the meaning of the expressions and phrases used in it and therefore to analyse how the parties wanted the text to be applied under the circumstances related to a given question of interpretation.1

A look at the relevant literature and the cases decided by the International Court of Justice concerning the field of interpretation proves that the main problems arise especially regarding two basic questions. Primarily, who should be the actors in the process of interpretation and secondly, methodical considerations of how interpretation should be carried out.

(b) As an important aspect of those two problems, it should not be overlooked, that the State sovereignty is fundamental for all further considerations. Thus, the most important actors of interpretation are the States, which also express their interpretation simply by applying the treaty. If problems of interpretation occur, it is the States decision of how to provide a proper way of dispute settlement. Nevertheless, unlike the legal questions of municipal law, where normally the decisions of courts are binding for everybody, in international law divergent opinions of interpretation persist if the power to decide with a legally binding effect is not transferred to another institution, e.g. international courts or tribunals. Provisions of that kind are normally included in the treaty itself to prevent further difficulties in the case of conflict. If decisions should not be binding, they may at least have a persuasive effect for the international community and the parties involved.

(c) Another aspect may be important in this context: although a dichotomy between ,,lawmaking treaties" and ,,contract-treaties" might not always be clear and useful from a general point of view,2 it is obvious that in the case of general multilateral treaties and treaties constituting international organizations, the interpretation carried by their organs, e.g. in the form of their practice, are undoubtedly of utter importance, even if it is not legally binding in every case.3 In this context it can be mentioned, that the International Court has used the practice of international organizations to interpret the competence of the General Assembly.4

However, this kind of interpretation may have limited binding effects for members, which were outvoted in the organs of the organization in question.5

(d) Resuming it may be stated, that the relevant actors of interpretation can be the parties, international courts or tribunals or the organs of international organizations.

(e) As for the methods of interpretation, it seems to be more helpful to consider them as flexible instruments of interpretation rather than to try to captivate them in a fixed code, which then may not be applicable because of the peculiarities in a given situation. This was also the point of view of the International Law Commission, which restricted itself to elaborate a few general principles of interpretation and giving room to the adaptation to the specific circumstances.6 It seemed clear, that the matter was to analyse the original intention of the parties.

(f) Finally, the textual approach was adopted in the articles 31 and 32 of the Vienna Convention: the subject of interpretation is the intention as expressed in the text, which ,,shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty" 7 , unless this ,,results in a meaning incompatible with the spirit, purpose, context for the clause or instrument in which the words are contained." 8 This ordinary meaning is determined by the given context and as a consequence, it looses its relevance when the context makes clear, that the parties wanted a term to have a different meaning.9 However, the State referring to such a special meaning will have the burden of proof.10 The context itself is not only predetermined by the text of the treaty, but also by preamble, annexes and other documents related to the treaty. All those sources have to be seen ,,in the light of the rules of general international law, in force at the time of its conclusion and in the light of the contemporaneous meaning of the terms" and "in the light of the purpose of the treaty." 11

(g) According to the Vienna convention subsequent agreements between the parties have to be taken into account.12

(h) As mentioned above, the subsequent practice too has a certain value in matters of interpretation. This is not only the case in international organizations but also concerns the practice by individual parties, although only to a certain extent, that varies from case to case.

(i) As supplementary means of interpretation the Vienna Convention mentions the preparatory work (travaux pr é paratoires) of the treaty and the circumstances of its conclusion, which may serve in order to confirm the first approach of textual interpretation or to clarify and correct it in case of doubts. The European Court of Human Rights has also used the changing social conditions as a mean of interpretation.13

(j) Generally, the International Court of Justice has made little use of teleological and historical considerations in his cases of treaty interpretation. This is naturally also due to the complex situations it has to deal with, which would offer an incredible variety of completely different and mostly elusive arguments. On the other hand, the European Court of Justice has used various clauses of the EC treaty to anticipate the development of the Communities in a considerable independence of the intentions laid down in the text.14

(k) Some general principles of interpretation have also found their way into international law jurisprundence.15 In the case of ambiguity of an expression used in a treaty, the meaning less onerous - ie causing less interference with the principle of State sovereignity - for the party who proposed the clause is to be preferred.16 If a party, on the other hand, has included a provision in favour of his interests, the interpretation which includes the least advantage should be preferred.17 Further, it is deemed that the parties wanted the clauses to express a certain meaning and to be effective in that sense.18 The last principle to be mentioned in this context is the rule generalia specialibus non derogant.19

(l) Another aspect of interpretation is included in Article 33.1 of the Vienna Convention: when a treaty is authentic in more than one language, the text is equally authoritative in each language. Nevertheless, there are still problems arising in the case that the draft was elaborated in one language and then translated into the other authentic versions.20

(m) Although the foregoing essay has shown some of the most important principles of treaty interpretation in international law, it is still recommendable to remind of the problems concerning the application of those principles in a particular case. There is no way to avoid a different approach from case to case in order to achieve a proper interpretation of legal texts, although this may lead, on the other hand, to certain insecurities and an unpredictability of court decisions. Especially in the case of multilateral agreements or treaties involving international organizations21 there are new questions arising constantly, which require new considerations in the field of interpretation.


Oppenheim ´ s International Law (9th edition), Longman, UK 1992

Ian Brownlie, Principles of Public International Law (5th edition), Oxford Press, UK 1998

Encyclopaedia of Public International Law, Max Planck Institute for Comparative Public Law and International Law, North Holland, Netherlands, 1995

Diez de Velasco, Instituciones de Derecho Internacional Publico (11th edition) Tecnos, Spain, 1997


1 In fact, it is unquestionable, that treaty interpretation is the most important case of interpretation in international law. Other possibilities may concern unilateral declarations of States, decisions or resolutions of international organizations. Whether and how rules of customary law can be subject to certain clarifications that might be akin to interpretation, seems to be still under discussion. (See Encyclopaedia of Public International Law, p 1417)

2 See Principles of Public International Law, pp 638 : ...the Commission and the Vienna Convention treat the law of the treaties as essentially a unity...[and]...jurists are today less willing to accept the more doctrinal versions of the distinction between treaty-contract (vertrag) and treaty-law (vereinbarung)...

3 See examples given in Encyclopaedia of Public International Law, p 1417, concerning the United Nations Security Council, the United Nations General Assembly, IMF and others.

4 ICJ Rep (1950), p 9

5 Principles of Public International Law, p 635

6 Historically, the first systematical approach to the field of interpretation is of roman origin. (Grotius and his successors). Later e.g. Emilio Betti tried to introduce uniform principles which, however, are considered hardly convincing because of the problems mentioned above.

7 Article 31 of the Vienna Convention

8 South West Africa Cases, ICJ Rep (1962), pp 335-6

9 Advisory Opinion on the Western Sahara, ICJ Rep (1975), pp 12,53. In this context, it should also be mentioned, that the ejusdem generis rule - applied by the ICJ in various cases - says, that general words which are textually closely connected to a special term, are bound in their interpretation by the meaning of the special term involved.

10 ibid

11 Oppenheim ´ s International Law, p 1281

12 This comprises formal amendments as well as informal agreements in matters of treaty application.

13 Encyclopaedia of Public International Law, p 1421

14 eg in the field of the protection of the environment, even before this task was included in the treaty expressis verbis.

15 In order to avoid interference with special methods of interpretation in different countries, this can only be admitted when the rules constitute generally accepted rules of jurisprudence. (Oppenheim ´ s International Law, p 1281)

16,, In dubio mitius"

17 ,,contra proferentem"

18 "ut res magis valeat quam pereat" In ICJ Rep (1952), p105 the Court admits that also apparently superfluous words may occur in a text, although this was the case of a unilateral declaration and not the result of negotiations.

19 However, it may not always be clear, which of various provisions is the special one.

20 Encyclopaedia of Public International Law, p 1421

21 eg the interpretation of the EC treaty

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Treaty Interpretation in International Law
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Matthias Klissenbauer (Author), 2001, Treaty Interpretation in International Law, Munich, GRIN Verlag,


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