Treaties — Formation, Validity, Termination (Vienna Convention)

A treaty is the most important deliberate source of international obligation. The codifying instrument is the Vienna Convention on the Law of Treaties, signed at Vienna on 23 May 1969 and in force from 27 January 1980 — frequently abbreviated as VCLT. The Convention partly codifies pre-existing customary international law and partly develops it; large parts of the Convention (the rules on interpretation, on material breach and on fundamental change of circumstances among them) are widely accepted as reflecting custom and bind even States that have not ratified the Convention. The Convention regulates the life-cycle of a treaty: how it is concluded, when it is valid, what it means once in force, and how it ends.

This chapter walks through the life-cycle in the order the Convention itself adopts. It is a foundational module of the International Law for Judiciary series and connects backward to the chapter on sources of international law (where treaties stand under Article 38(1)(a) of the ICJ Statute) and forward to the chapters on customary international law (the principal alternative source) and on the Indian Constitution and international law (where the dualist tradition determines how a ratified treaty enters Indian municipal law).

Definition and scope of the Convention

Article 2(1)(a) of the Vienna Convention defines a treaty as "an international agreement concluded between States in written form and governed by international law, whether embodied in a single instrument or in two or more related instruments and whatever its particular designation." Three elements are essential: it must be an agreement (mere parallel statements do not suffice); it must be written (oral agreements are excluded from the Convention's framework, although Article 3 preserves their international validity); and it must be governed by international law (commercial agreements between States that the parties have chosen to govern by some municipal law are excluded). Designation does not matter — a convention, treaty, agreement, protocol, exchange of notes, statute, charter, covenant, declaration or memorandum of understanding may all qualify provided the substance satisfies the definition.

The 1969 Convention covers treaties between States only — leaving aside the question of which international entities other than States have the legal personality required to conclude treaties, a matter taken up in the chapter on the subjects of international law. The companion instrument — the Vienna Convention on the Law of Treaties between States and International Organizations or between International Organizations 1986 — extends comparable rules to treaties to which international organisations are parties. Article 3 of the 1969 Convention preserves the international validity of agreements that fall outside its scope.

Pacta sunt servanda — the foundational rule

The fundamental principle of treaty law is that treaties are binding upon the parties to them and must be performed in good faith — pacta sunt servanda — reaffirmed in Article 26 of the Convention. Without a baseline assumption that States will perform their treaty obligations in good faith, there would be no reason for States to enter into such obligations at all. Article 27 reinforces the rule by providing that a party may not invoke the provisions of its internal law as justification for its failure to perform a treaty. The pacta sunt servanda rule is jurisprudentially among the oldest principles of international law and supplies the moral and practical foundation for the Convention as a whole.

Formation — capacity, full powers, consent

Capacity and full powers

States have the capacity to conclude treaties — Article 6 of the Convention confirms the position. The act of conclusion is performed by individuals representing States, and Article 7 requires such representatives to produce "full powers" — documents from the competent authorities of the State certifying the representative's status to negotiate, adopt or authenticate the text or to express the State's consent to be bound. The requirement of full powers protects the other parties against the risk of dealing with someone who lacks authority to bind. Three categories of officials are exempt from the requirement of producing full powers, by virtue of their position: heads of State, heads of government and ministers for foreign affairs (for all acts relating to the conclusion of a treaty); heads of diplomatic missions (for adopting the text of a treaty between their State and the receiving State); and representatives accredited to international conferences and organisations (for adopting the text of a treaty in that conference or organisation).

Adoption and authentication of the text

Articles 9 and 10 govern the adoption and authentication of the treaty text. Adoption at an international conference takes place by the vote of two-thirds of the States present and voting unless they decide by the same majority on a different rule. Authentication — the formal process by which the text is established as definitive — is by the procedure laid down in the treaty itself, by signature, signature ad referendum or initialling by the representatives of the States. After authentication, the text is fixed; the only further question is whether the State will consent to be bound by the text.

Modes of expressing consent to be bound

Article 11 lists the principal modes by which a State may express its consent to be bound by a treaty: signature, exchange of instruments constituting a treaty, ratification, acceptance, approval or accession — and any other means agreed by the parties. The most important of these in modern practice is ratification, examined separately below. Signature alone may suffice for routine and less politically sensitive treaties (Article 12). Pending ratification, signature carries an interim obligation under Article 18: the State must refrain from acts which would defeat the object and purpose of the treaty until it has made clear its intention not to become a party.

Ratification

Ratification is the act by which the competent constitutional authority of the State formally confirms the State's willingness to be bound. Article 14 stipulates that ratification will express consent to be bound where the treaty so provides, where the negotiating States agreed that ratification should be required, or where the representative signed subject to ratification or such an intention appeared from the full powers or was expressed during negotiations. The internal procedure for ratification varies from State to State and is a matter for each State's constitutional law: in the United Kingdom the prerogative power lies with the Crown, subject to a parliamentary practice of laying significant treaties before Parliament; in the United States the President ratifies on the advice and consent of two-thirds of the Senate; in India the executive ratifies under Article 73 of the Constitution but legislation is required under Article 253 to give the treaty domestic effect — a position taken up at length in the chapter on the constitutional treatment of treaties under Articles 51 and 253.

Reservations

A reservation, defined in Article 2(1)(d) of the Convention, is a unilateral statement made by a State when signing, ratifying, accepting, approving or acceding to a treaty, whereby the State purports to exclude or to alter the legal effect of certain provisions of the treaty in their application to that State. Reservations reflect the principle of State sovereignty: a State may refuse its consent to particular provisions while accepting the bulk of the treaty. The price is fragmentation — a treaty riddled with reservations may dilute the uniformity that multilateral law-making aims to achieve.

Permissibility

Article 19 sets the framework. Reservations may be made except where the treaty prohibits them, where the treaty allows only specified reservations and the proposed reservation is not among them, or where the reservation is incompatible with the object and purpose of the treaty. The object-and-purpose test crystallised in the International Court's advisory opinion in Reservations to the Genocide Convention (ICJ Reports 1951): a State that has made a reservation objected to by some parties but not others may be regarded as a party to the Convention if the reservation is compatible with its object and purpose. The test displaced the older League-of-Nations rule that required the unanimous consent of the other parties.

Acceptance, objection and effect

Article 20 distinguishes three positions a State may take towards a reservation made by another. Acceptance establishes the reserving State as a party to the treaty in relation to the accepting State. An objection that does not preclude entry into force has the effect, under Article 21(3), of rendering the provisions to which the reservation relates inapplicable as between the two States to the extent of the reservation. An objection that does preclude entry into force prevents the treaty from coming into force as between the objecting and reserving States. A reservation is deemed to have been accepted if no objection has been raised within twelve months of its notification or by the date of consent to be bound, whichever is later.

The position with regard to human rights treaties has been controversial. The European Court of Human Rights in Belilos v. Switzerland (1988) and the UN Human Rights Committee in General Comment 24 (1994) have taken the view that an impermissible reservation to a human rights treaty may be severed, leaving the reserving State bound by the treaty in full — an approach explored further in the chapter on international human rights law. The International Law Commission, in its Preliminary Conclusions on Reservations to Normative Multilateral Treaties of 1997, reaffirmed the applicability of the Vienna regime to human rights treaties while accepting that monitoring bodies are competent to comment on the admissibility of reservations.

Entry into force, observance and interpretation

Entry into force

Article 24 provides that a treaty enters into force in the manner and on the date specified in the treaty itself or as the negotiating States have agreed. In the absence of such a provision, a treaty enters into force as soon as consent to be bound has been established for all negotiating States. Multilateral treaties commonly stipulate entry into force after the deposit of a fixed number of ratifications: the Vienna Convention on the Law of Treaties itself entered into force thirty days after the thirty-fifth instrument of ratification was deposited; the Rome Statute of the International Criminal Court required sixty ratifications. Article 25 permits provisional application pending entry into force where the treaty so provides or the parties so agree.

Observance and the rule against invoking municipal law

Article 26 codifies pacta sunt servanda. Article 27 provides that a party may not invoke the provisions of its internal law as justification for its failure to perform a treaty — subject to a narrow exception in Article 46 for the case of consent given in manifest violation of an internal law of fundamental importance regarding competence to conclude the treaty. Article 28 establishes the presumption of non-retroactivity. Article 29 establishes the presumption that a treaty applies to the entire territory of each party.

Interpretation

Articles 31 to 33 codify the rules of treaty interpretation. The general rule in Article 31 is that a treaty is to 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. Context includes the text, the preamble and any annexes, together with any agreement relating to the treaty made by all the parties in connection with its conclusion. Subsequent agreement and subsequent practice in the application of the treaty are taken into account, as are any relevant rules of international law applicable in the relations between the parties. Article 32 permits recourse to supplementary means of interpretation, including the preparatory work (travaux préparatoires) and the circumstances of the conclusion, to confirm the meaning resulting from Article 31 or to determine the meaning where Article 31 leaves it ambiguous, obscure or absurd. Article 33 governs treaties authenticated in two or more languages.

Validity — grounds of invalidity

Part V of the Convention sets out the grounds on which the validity of a treaty may be questioned. The grounds fall into two clusters: defects of consent (Articles 46 to 52) and incompatibility with peremptory norms (Article 53).

1. Manifest violation of internal law (Article 46). A State may invoke a violation of its internal law on competence to conclude treaties only if the violation was manifest and concerned a rule of fundamental importance.
2. Specific restrictions on authority of the representative (Article 47). Where the authority of a representative was subject to a specific restriction not notified to the other States, the State may not invoke the omission unless the restriction was notified before the consent was expressed.
3. Error (Article 48). A State may invoke an error in a treaty as invalidating its consent if the error relates to a fact or situation assumed by the State to exist at the time the treaty was concluded and formed an essential basis of consent — provided the State did not contribute to the error.
4. Fraud (Article 49). Consent procured by the fraudulent conduct of another negotiating State may be invalidated.
5. Corruption of the representative (Article 50). Consent procured by the direct or indirect corruption of the representative of a State may be invalidated.
6. Coercion of the representative (Article 51). Consent procured by the coercion of the representative through acts or threats directed against him is without legal effect.
7. Coercion of the State by threat or use of force (Article 52). A treaty is void if its conclusion has been procured by the threat or use of force in violation of the principles of international law embodied in the Charter of the United Nations.
8. Conflict with a peremptory norm — jus cogens (Article 53). A treaty is void if, at the time of its conclusion, it conflicts with a peremptory norm of general international law from which no derogation is permitted. The category — examined further in the chapter on customary international law and Article 38(1)(c) general principles — covers the prohibitions on aggression, genocide, slavery, torture and crimes against humanity.

Defects of consent under Articles 46 to 50 produce voidability — the treaty stands until the affected State chooses to invoke the defect. Coercion (Articles 51 and 52) and conflict with jus cogens (Article 53) produce nullity ab initio.

Termination, suspension and withdrawal

Part V also regulates the ways in which treaty obligations come to an end. Articles 54 to 64 set out the grounds.

1. Termination by treaty terms or by consent (Articles 54 and 57). A treaty may be terminated, or a party may withdraw, in conformity with the provisions of the treaty itself or at any time by consent of all the parties after consultation with the other contracting States.
2. Implied right of denunciation (Article 56). A treaty containing no provision on termination, denunciation or withdrawal is not subject to denunciation or withdrawal unless it is established that the parties intended to admit such a possibility or such a right may be implied from the nature of the treaty. A party seeking to invoke the implied right must give not less than twelve months' notice.
3. Material breach (Article 60). A material breach of a bilateral treaty by one party entitles the other to invoke the breach as a ground for terminating the treaty or suspending its operation. A material breach of a multilateral treaty entitles the other parties acting unanimously to suspend or terminate the treaty either between themselves and the defaulting State or between all parties; a specially affected party may invoke the breach as a ground for suspension as between itself and the defaulting State; and any party other than the defaulting State may invoke the breach as a ground for suspension if the treaty is of such a character that a material breach of its provisions by one party radically changes the position of every party with respect to the further performance of its obligations.
4. Supervening impossibility of performance (Article 61). A party may invoke the impossibility of performing a treaty as a ground for terminating or withdrawing from it if the impossibility results from the permanent disappearance or destruction of an object indispensable for the execution of the treaty.
5. Fundamental change of circumstances — rebus sic stantibus (Article 62). A fundamental change of circumstances which has occurred with regard to those existing at the time of the conclusion of a treaty, and which was not foreseen by the parties, may not be invoked as a ground for terminating or withdrawing from the treaty unless the existence of those circumstances constituted an essential basis of the consent of the parties to be bound and the effect of the change is radically to transform the extent of obligations still to be performed under the treaty. The doctrine does not apply to treaties establishing a boundary, and may not be invoked by a party whose own breach occasioned the change. The Court applied the doctrine narrowly in Gabčíkovo-Nagymaros Project (Hungary/Slovakia, ICJ Reports 1997) — a decision featured in the survey of leading ICJ rulings of Indian interest.
6. Severance of diplomatic or consular relations (Article 63). The severance of diplomatic or consular relations does not of itself affect the legal relations established between the parties by a treaty, except in so far as the existence of such relations is indispensable for the application of the treaty.
7. Emergence of a new peremptory norm (Article 64). If a new peremptory norm of general international law emerges, any existing treaty in conflict with that norm becomes void and terminates.

Indian municipal-law interface

India is not a party to the Vienna Convention on the Law of Treaties 1969, but its rules on interpretation, material breach and fundamental change of circumstances are widely accepted as reflecting customary international law and apply to India in that capacity. Treaty-making power in India lies with the executive under Article 73 of the Constitution; Article 253 empowers Parliament to legislate for implementing any treaty, agreement or convention with another country. India follows the dualist tradition: a ratified treaty does not, of its own force, become part of Indian municipal law and does not bind individuals within India unless and until Parliament has legislated to give it effect. The deeper position is taken up in the chapter on the implementation of international treaties in Indian courts. Even within the dualist framework, the Supreme Court has used unimplemented treaties as interpretive aids: Vishaka v. State of Rajasthan (1997) 6 SCC 241 drew directly on the Convention on the Elimination of All Forms of Discrimination Against Women to formulate guidelines on workplace harassment, and Gramophone Co. of India v. Birendra Bahadur Pandey (1984) 2 SCC 534 read Indian copyright law harmoniously with India's obligations under the Berne Convention.

Conclusion

The Vienna Convention on the Law of Treaties 1969 supplies the comprehensive code by which treaty obligations are made, performed and unmade. The architecture is clean. Treaties are concluded by representatives with full powers; they bind only on consent expressed by signature, ratification, acceptance, approval or accession; reservations may be made within the object-and-purpose limit; the treaty enters into force as the parties have agreed and is to be performed in good faith; interpretation follows the ordinary meaning in context and in the light of object and purpose; validity may be challenged for defects of consent or incompatibility with jus cogens; termination may follow from the treaty's own terms, from consent, from material breach, from supervening impossibility, from fundamental change, or from the emergence of a new peremptory norm. Above the Convention sits the principle of pacta sunt servanda — the rule that gives the entire structure its moral and practical force. The chapter on the customary law and general principles develops the alternative source against which treaty obligations are read; the chapter on landmark ICJ decisions illustrates the application of the Vienna regime in contentious litigation between States, including in cases of direct concern to India.

Frequently asked questions

Is India a party to the Vienna Convention on the Law of Treaties 1969?

No. India has signed neither the 1969 Vienna Convention on the Law of Treaties nor the 1986 Convention on Treaties between States and International Organizations. However, large parts of the 1969 Convention are widely regarded as reflecting customary international law — the rules on interpretation in Articles 31 to 33, the rule on material breach in Article 60 and the doctrine of fundamental change of circumstances in Article 62 are leading examples — and bind India in that capacity. India's treaty-making power is exercised by the executive under Article 73 of the Constitution, and Parliament gives ratified treaties domestic effect through legislation under Article 253.

What is a reservation to a treaty and when can it be made?

A reservation is a unilateral statement made by a State when signing, ratifying, accepting, approving or acceding to a treaty, by which the State purports to exclude or alter the legal effect of certain provisions of the treaty in their application to that State. Article 19 of the Vienna Convention permits reservations except where the treaty itself prohibits them, where the treaty allows only specified reservations not including the one proposed, or where the reservation is incompatible with the object and purpose of the treaty. The object-and-purpose test was laid down by the International Court of Justice in its 1951 advisory opinion on Reservations to the Genocide Convention.

What is the difference between voidability and nullity under the Vienna Convention?

Defects of consent under Articles 46 to 50 of the Convention — manifest violation of internal law, specific restrictions on authority, error, fraud and corruption of the representative — make a treaty voidable. The treaty stands and remains in force until the affected State chooses to invoke the defect. Coercion of a representative under Article 51, coercion of the State by the threat or use of force under Article 52, and conflict with a peremptory norm of general international law under Article 53 produce nullity ab initio: the treaty is void from the outset and cannot be cured by acquiescence or subsequent ratification.

What is the doctrine of rebus sic stantibus and when does it apply?

The doctrine of rebus sic stantibus — codified in Article 62 of the Vienna Convention — permits a party to invoke a fundamental change of circumstances as a ground for terminating or withdrawing from a treaty, but only on stringent conditions. The change must be of circumstances that existed at the time of the conclusion of the treaty; it must not have been foreseen by the parties; the existence of those circumstances must have constituted an essential basis of the parties' consent to be bound; and the effect of the change must be radically to transform the extent of obligations still to be performed. The doctrine does not apply to boundary treaties and may not be invoked by a party whose own breach occasioned the change.

What is a material breach of a treaty under Article 60?

Article 60(3) of the Vienna Convention defines a material breach as either a repudiation of the treaty not sanctioned by the Convention or the violation of a provision essential to the accomplishment of the object or purpose of the treaty. The consequences of a material breach depend on whether the treaty is bilateral or multilateral. In a bilateral treaty, the other party may invoke the breach to terminate the treaty or suspend its operation. In a multilateral treaty, the other parties acting unanimously may suspend or terminate as between themselves and the defaulting State or between all parties, and a specially affected party may invoke the breach to suspend the treaty as between itself and the defaulting State.