This article is written by Mehak Jain from Hidayatullah National Law University. This is an exhaustive article that aims to explain the concept of treaties and their position in international law, and the Vienna Convention on the Law of Treaties.


Article 38(1) of the International Court of Justice’s statute identifies treaties as a source of law, along with general principles and customs. Treaties occupy a very eminent position in international law. They ensure friendly and peaceful relations of states with one another and are a means by which international organizations take form, regulate and monitor their affairs. The concept of the treaty has undergone significant changes over time. In earlier periods, treaties used to be oral and a ceremony would be held where the parties would conclude it and swear an oath to God, which used to act as the binding force of the treaty. Now, treaties must be written and are legally binding between its parties.

Drafted by the International Law Commission of the UN and taking force on 27 January 1980, the Vienna Convention on the Law of Treaties set out some fundamental rules as to how treaties are to operate and take form. More than half of the member states of the UN are a party to the Convention.

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Concept of treaty

Treaty in common parlance may be defined as written agreements between parties, which may or may not be stated, to identify and follow a set of rules. They may also be referred to as pacts, agreements, charters, etc. Declarations and political statements are excluded from the scope of the definition of a treaty.

Treaties have been classified on the basis of many principles. On the basis of the object, they have been classified as political treaties (including alliances and disarmament treaties), constitutional and administrative treaties (e.g. WHO’s constitution, which is responsible for setting up the international body and to regulate it affairs), commercial treaties (trade and fishery agreements), criminal treaties (which define certain international crimes and may require the offender to be extradited), treaties codifying international law, and treaties for ensuring civil justice.

A country that hasn’t signed the treaty has no obligation to follow its norms. However, like the ICJ had stated in the North Continental Shelf Cases, that some treaties may give rise to international conduct,  customs and be of a “fundamentally norm-creating character.” Article 26 of the Vienna Convention on the Law of Treaties deals with the Latin maxim “pacta sunt servanda”, i.e. every signatory is to follow the treaty in good faith and is binding upon them. This forms the basis of every international agreement.

“Reservations” are the way in which a signatory may escape having to follow all the provisions of the treaty and is a tactic used  to become a party by agreeing to the basic principles of a treaty. However, reservations can only be made in cases where such reservation is not contrary to the object of the treaty.

Interpretation of a treaty should be bona fide and the object and purpose of the treaty needs to be kept in mind while doing so. In case the text is vague, “travaux preparatories” and other supplementary means of interpretation might be used. One such method of interpretation of a treaty is adopting a broader-purpose approach. Contrastingly, a purpose-oriented approach is adopted in cases where the treaty in question to be interpreted is the constitutional document of an international organization.
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Kinds of treaty

Law Making treaties

The term “law-making” treaty seems to be confusing, as it raises the question- Can treaties create law? This term actually refers to the content and the subject matter of a treaty, which instead of being contractual shall be statutory. The emergence of a subsisting need of international legal order sparked a newfound interest in this type of treaty. The need of bringing rules which had statutory force was felt rather than the existing rules which governed voluntary legal relations between states. In cases of law-making treaties, the obligations are independent; they don’t require a subsequent fulfilment of rules by other parties to it. These obligations have binding force and the parties to these treaties must follow it. Unlike contracts, treaties have the power to make new international tribunals, international waterways, mandates, etc.

These are multilateral treaties which stand for a common cause. A commentary by Fitzmaurice takes human rights treaties and maritime regimes as law-making treaties. In the case of a multilateral treaty, this type of treaty can be broken down and thought of as a number of bilateral treaties, each of which are independent of one another and have to follow the obligations inherently. As for bilateral treaties, they can simply be viewed as dependent on each other as existence. Here, each party does not join to provide another party something it might require, but rather to stand for a mutual cause or support a rule binding on all.

Contractual treaties

They are usually applicable to treaties having a small number of parties and are most commonly seen in bilateral treaties. These are treaties where parties are mutually dependent on each other for specific treatment to gain benefits, and have rights and obligations towards each other. In reality, treaties need to take care of both the statutory as well as the contractual function. The scope of treaties is mostly perceived in a contractual framework. Unlike law-making treaties, which sets out rules for conduct, rights, and duties between parties which have to take effect on the conclusion of the treaty, contractual treaties are usually limited to, say, exchange of goods which one state might not possess and require, or conveyances. Here, one party agrees to provide the other party something it needs for something else in return, thereby forming a system like barter.

Types of treaty

Bilateral treaties

Treaties involving two entities are bilateral treaties. It is not necessary that the treaty can only have 2 parties; there may be more than two parties, however, there should be only two states involved. For example, the bilateral treaties between Switzerland and the European Union(EU) have 17 parties, which are divided into two parts, the Swiss and the EU and its member states. It is important to note that by virtue of this treaty, obligations, and rights arise between the two entities to it, i.e. the EU and the Swiss. This treaty does not give rise to obligations between the EU and its member states.

Multilateral treaties

Treaties between three countries or more are multilateral treaties. They might be international or domestic. They give rise to rights and obligations among all the parties, i.e. each signatory has obligations towards all the other signatories.

Treaties with a higher number of participating states gain more international significance since it reflects the importance of the treaty. However, there have been many crucial bilateral treaties too, such as those emerging from Strategic Arms Limitation Talks. All treaties have different purposes. Some set up international organizations through the UN Charter of 1945, whereas others deal with issues such as visa regulations. 

The binding force of Treaties

Vienna Convention on the Law of Treaties,1969

The International Law Commission of the United Nations drafted the Vienna Convention on the Law of Treaties, which was adopted on May 23, 1969. Entering into force on January 27, 1980, it is an international agreement between the states to govern and regulate treaties.

The treaty is limited to and encompasses written treaties only. Divided into many parts, the first part sets out the object, terms, and scope of the agreement, and the second part lays down rules for adoption, ratification, the conclusion of the treaties. The third part deals with the interpretation of treaties. The fourth part talks about the modification of treaties, and lastly, the fifth part delves into withdrawal, suspension, termination, and invalidation of a treaty. It also includes a  necessary clause which gives the International Court of Justice jurisdiction over any possible disputes. The final parts discuss rules for ratification and effects on treaties due to change in government.

The document has not been ratified by the US, however, it follows its provisions usually. Till 1979, all the 35 member states of the UN had ratified the treaty.

As per the Latin maxim “pacta sunt servanda”, or as mentioned under Article 26 of the Convention, all treaties are binding on its signatories and shall be followed bona fide. The binding nature which this treaty serves to all other treaties is a reason why the US isn’t a part of it. There exists a tussle between Congress and the Executive branch, over who has the authority to validate a withdrawal from treaties on behalf of the country. Since treaties are binding, there is too much at stake between the two organs of the US government.


Article 1 of the said Convention says that it is applicable to treaties between the states. It is also applicable to treaties entered into by international organizations. The Convention defines “treaty” as a written agreement between states which may be embodied in one or more than one instrument and is governed by International law. Article 2 further defines “ratification”, “approval”, “reservation”, etc. in the context of the treaty. It is important to note that none of the provisions of the said Convention are applicable to written agreements between an international body and a state, or between 2 subjects of international law. Article 3 thereby reiterates the scope of the Convention and states that if such an agreement has been entered, its legality would not be affected. The parties to such agreements do not have to follow the rules of the Convention either, however, they should ensure that the rules they follow to govern the treaty are acceptable in the eyes of international law. Such agreements shall also not have any effect on the relations between the States.

Role of treaties in International Law

Treaties form the basis of international law. They maintain stability and diplomatic relations between the States. They are thus the most important elements to guarantee international cooperation, peace, and security. This is one of the reasons why treaties are regarded as the fundamental source of international law. The preamble of the Vienna Convention on the Law of Treaties accords to treaties with the eminent position they hold in ensuring international order and emphasizes their existence as a continuum.

Treaties go as back into the past as one can remember. Perhaps, one of the first treaties ever known was the one created by rulers of Hittite with Ramesses II, who was the King of Egypt. The treaty between Kings of Elba and Ashur is the oldest treaty preserved in full text. It is said to be concluded in the third century BC. In earlier times, there was no concept of State and there was the existence of many sovereigns. At that time, treaties weren’t only between different states but also between officials of different ranks, or between other authorities. Swearing to God was what acted as the binding force at that time. As time passed by, the way in which treaties were concluded gradually became more streamlined and sophisticated. Treaties started taking the written form rather than being oral as in the earlier times. Treaties that dealt with subjects of peace and alliance began dominating and could now be given the force of a statute, for example, the Statum in favorum principum. As the world started settling as states, treaties began gaining prominence. The creation of the international organizations gave treaties new-found importance. Then came the Law of Treaties which set into permanence and recorded treaties as being a source of international law.


Parties to a treaty

There are two types of parties to a treaty- state parties and third States. A state party has ratified and signed the treaty and is legally bound to follow it. “Third state” has been defined as a state which is not a party to the treaty. 

Third States

Article 34 of the Convention says that a third State shall be free from any rights or obligations to a treaty. In case of treaties having a provision to extend obligations to a third State, such provision must have obtained the express consent of that third State for it to apply to them. Provided that the third state gives its consent, if the parties to a treaty wish to confer rights upon a third state/ group of states to which it belongs/all states, a right shall arise for the third state. This is mentioned in Article 36 of the Convention. A state which shall exercise this right conferred on it by the treaty must follow the directions and conditions as mentioned in it too. Article 37 deals with revocation/alteration of rights and obligations of third states and says that unless otherwise agreed, the obligation on the third State by virtue of Article 35 may be revoked/altered if express consent of parties to the treaty and the third state has been obtained. However, in case of a right conferred by Article 36, the same may not be revoked/altered by the parties if it was pre-decided that such right shall not be revocable/open to alteration without the consent of the third State. Lastly, by virtue of the customary rule of international law, rules of a treaty become binding even on third States.

Formation of a treaty

There is no concrete way of creating a treaty. It may be presented in different forms such as a contract or an exchange of notes, as seen in the Rush-Bagot Agreement between Great Britain and the U.S. for mutual disarmament on the Great Lakes. Most treaties, however, follow a similar structure. Every treaty begins by introducing its preamble, which states the object of the treaties and the parties to it. It is then followed by what the parties agreed upon. A statement of the period may or may not follow; it depends on the time period for which the treaty shall exist. Next up, reservations and then ratification clauses follow. Then, it ends with the signatures of the parties involved along with the date and venue of ratification.

Additional articles may be further attached along with the declaration that they are equal in value as to other clauses. Going by the Law of Treaty, the following steps form the essentials of formation of a treaty-

  • Adoption of the text

Consent of all parties to a treaty is essential for adopting a text. If the treaty is being adopted at an international conference, a two-thirds majority shall be required for the adoption of text unless agreed upon otherwise.

  • Authentication of the text

As per the procedure mentioned in the text, a treaty shall be established to be authentic. On the failure of such procedure, signatures or initials of representatives of the participating states may be sufficient to deem the text to be definitive.

  • Expression of consent

This may be by way of signatures, ratification, acceptance, approval or accession or by exchanging instruments required for the treaty.

  • Consent by signature

Provided that the treaty explicitly states that signature by the representative of a state shall be sufficient to be declared as a party, or the negotiating states have mutually consented to signature be sufficient, the representative’s signature expresses a state’s full intention to enter into a treaty.

  • Consent by exchange of instruments required by the treaty

If the states agree that exchange shall be equivalent to the expression of the consent to enter into the treaty, then so shall be the case.

  • Consent by ratification, acceptance or approval

If the negotiating states are of the opinion that ratification shall be equivalent to expressing consent, or the treaty provides for ratification, then it shall be an acceptable way of obtaining consent to the treaty. Similarly, the same condition applies to consent expressed by approval or acceptance.

  • Consent expressed by accession

Consent to the treaty shall be obtained If the treaty provides for it or the negotiating states agree upon accession.

  • Formulation of reservations

A state may while concluding the treaty expresses its reservations unless it’s prohibited by the treaty, or if permitted shall violate with the object and intent of the treaty.

Invalidity of treaty

Part V of the Vienna Convention on The Law of Treaties, 1969, particularly Section 2 deals with the invalidity of treaties. Articles 46-53 set out the ways to invalidate a treaty, i.e. make them void and unenforceable under international law. There are several reasons as to why an internationally binding treaty may be declared as invalid. One of the reasons for invalidity is that they might be riddled with problems ever since the time of formation. Content of the treaties and the mode by which consent is obtained are the two grounds on which treaties may be invalidated.

It is important to note that invalidation is different from withdrawal and termination; the former involves invalidation of consent right from the start, while the latter involves future alteration in consent to be a signatory. 

  1. Ultra Vires treaties

Article 46 of The Law of Treaties talks about the willingness of a state to invalidate and conclude the treaty on the ground that it goes against its internal law. No State shall invoke such a fact. However, exceptionally, such fact may be invoked if the violation was manifest and of fundamental importance to the State’s internal law.

The Law of Treaties in its preamble clearly regards treaties as a source of international law. This has two meanings- one, no matter if an act is approved by the internal law, it will not assume legality if it is condemned under international law, and two, in case of conflict between internal and international law, international law shall prevail. 

  1. Error

Article 48 talks about invalidation on grounds of the presence of errors in a treaty. It is important to note that errors with respect to the wording of the text do not invalidate the treaty. If the error is to a substantial fact, i.e. one that was believed to be in existence at the time of signing the treaty and formed the basis for which the treaty was signed, such an error may be provoked by the state, provided that such state has not, by its own conduct, contributed towards the error.

  1. Fraud and Corruption

If a state has become a signatory to a treaty due to fraudulent act or conduct of another state who is also a signatory to the treaty, such a state may invoke invalidating the treaty on grounds of consent being obtained by fraud.

If a negotiating state, by corrupting the representatives of another state directly or indirectly, has induced such a state’s consent into entering a treaty, the state may invoke invalidating its consent to be bound by the treaty.

  1. Coercion

Consent shall also be invalidated if it is obtained by coercing the representative of a state, or by threatening the use of force against a state.

  1. Conflict with Jus cogens

Treaties that are in conflict with jus cogens, or “peremptory norm of general international law” such as piracy, genocide, apartheid, torture, etc are void.

Termination of treaty 


Obligations in international law arise from the consent of the state. This is why treaties are mostly non-binding in nature, and they expressly allow a party to withdraw. For example, the Single Convention on Narcotic Drugs says that the treaty shall be terminated if the total number of signatories falls below 40.

Article 56 deals with withdrawal from treaties without a termination/denunciation/withdrawal clause. According to this article, such a treaty shall not be denounced unless:

         –The intention of the parties as to the possibility of withdrawal was established.

         –A right of denunciation was implied in the treaty.

It must be brought to notice that not all treaties can be withdrawn from; it depends on the terms of the treaty. For example, when North Korea declared its intention to withdraw itself from the International Covenant on Civil and Political Rights, the United Nations Secretary-General held that the parties there was a reason why the treaty did not provide for a withdrawal cause and it wasn’t put in the treaty on purpose. North Korea wasn’t allowed to withdraw.

If one party withdraws from a bilateral treaty, the treaty ceases to exist. When one party withdraws from a multilateral treaty, there is no effect on the treaty, only such a state’s obligations as per the treaty end.

One instance where Article 46 of the Law of Treaties was invoked was the treaty between Israel and the United States for the withdrawal of Israel from the Sinai peninsula. The US promised to provide supply as well as defense equipment in return. However, the treaty was signed without taking the consent of the US Senate, and it was contested that the treaty was thus void as per domestic law. Moreover, since this violated the U.S. Constitution, the treaty was invalid on international grounds too.


Suspension and Termination

  1. Implied by the conclusion of a later treaty- 

On account of drafting a later treaty dealing with the same subject matter as its previous version, the previous counterpart shall be deemed to be terminated, provided that the parties intend to be governed by the new treaty or the provisions of both the treaties are so incompatible with each other that both the treaties cannot be applicable at the same time. The previous treaty will be terminated if it’s the implied or established intention of the signatories.

  1. As a consequence of its breach- 

There are different consequences for different kinds of treaties. If the treaty is bilateral and one of the parties has caused a material breach of the treaty, then the other may use it to bring the treaty to an end. If the treaty is multilateral, then default by one of the parties entitles the other parties to terminate/suspend such treaty, wholly or partly by unanimous consent. Material breach, as explicitly mentioned in Section 61 consists in the violation of a provision of the treaty which is of the essence to it and forsaking the treaty.

  1. Impossibility of performance-

The impossibility of fulfilling conditions as per the treaty is considered sufficient ground for the suspension/ termination of a treaty. If the impossibility is permanent, i.e. the devastation makes execution of the treaty impossible, the treaty may be terminated. However, if the impossibility is temporary, the treaty may be suspended for the required duration.

However, if the impossibility of performance is due to the conduct and action of one the parties, i.e. due to violation of a provision of the treaty or violation of any international obligations, the treaty may not be terminated/ suspended.

  1. Fundamental change of circumstances-

Unforeseen changes which fundamentally affect the treaty may be sufficient to invoke termination/ revocation of the treaty, provided that the changes are “fundamental” i.e. initial existence of the circumstances may affect the consent of parties to the treaty and that as a result, the obligations to be performed under the treaty have been changed and transformed radically.

If the change is due to breach of treaty or any international obligations by one of the parties to the treaty, then this article would not be invokable.

  1. Rift of diplomatic or consular relations

Provided that the treaty demands the existence of hostile and diplomatic relations between its parties, disturbance or severance of such relations shall have no effect on the treaty since it doesn’t really affect the legal relationship among the parties.

  1. Emergence of new jus cogens

If a new jus cogens or peremptory norm of general international law emerges after worldwide assent to it, any treaty in violation of it shall be deemed to be terminated.


The Vienna Convention on the Law of Treaties lays down basic and fundamental principles to govern treaties. The main principle on which the Convention operates is “pacta sunt servanda”, i.e. all treaties must be followed in good force. It provides for various provisions such as ratification, reservation, approval, conclusion, withdrawal, invalidation, termination of a treaty, etc. The Convention is legally binding on its parties. 

Treaties play an important role as the source of international law and occupy a colossal pedestal in this field.

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