Why This Matters
Every major obligation in international law is treaty-based: the UN Charter, UNCLOS, the VCDR, the Rome Statute. Understanding how treaties are formed, how consent is expressed, what reservations do to treaty obligations, and how treaties end is not a separate topic: it is the operating manual for every other chapter in this book. The VCLT (1969) governs the entire lifecycle of a treaty. The examiner tests formation and reservation together in Part B and generates Part C scenarios from the consequences of breach and the effects of reservations.
Chapter Overview
This chapter answers four questions:
- How are treaties formed? Negotiation, adoption, authentication, signature, ratification.
- How is consent expressed? Signature, ratification, accession, approval.
- What are reservations? Their definition, validity, and effect on treaty relations.
- How do treaties end? Termination by consent, breach, impossibility, fundamental change.
Definition and Classification of Treaties
A treaty is an international agreement concluded between states in written form and governed by international law, whether embodied in a single instrument or two or more related instruments.
This definition from Article 2(1)(a) VCLT identifies four elements: the agreement must be between states (or international organisations in later instruments), it must be in written form, it must be governed by international law, and its form is immaterial.
Treaties are classified by parties (bilateral or multilateral), by function (law-making treaties that create general rules versus contractual treaties creating specific reciprocal obligations), and by subject matter. Law-making multilateral treaties (UN Charter, UNCLOS, VCLT itself) are the primary instruments of international legislation.
Formation of Treaties
Treaty formation passes through five stages: negotiation, adoption of text, authentication, expression of consent to be bound, and entry into force.
Negotiation and Adoption
Negotiation occurs through plenipotentiaries: persons furnished with full powers (pleins pouvoirs) by their state to negotiate and conclude treaties. The head of state, head of government, and minister of foreign affairs are presumed to have full powers without producing credentials. Others must produce formal authorisation.
Adoption of the text is the formal act by which the negotiating states agree on the final form of the treaty. For bilateral treaties, adoption typically requires the consent of both parties. For multilateral treaties, Article 9 VCLT provides that adoption requires a two-thirds majority of the states present and voting unless a different rule is agreed.
Authentication
Authentication is the procedure by which the text of a treaty is established as authentic and definitive. It is typically done by signature, initialling, or incorporation in the Final Act of a diplomatic conference. Authentication does not create binding obligation: it merely fixes the text.
Entry into Force
A treaty enters into force when the conditions specified in the treaty for entry into force are met, typically on a specified date or when a required number of states have ratified.
Modes of Expressing Consent
A state expresses its consent to be bound by a treaty through one of four modes.
Signature: For some treaties, signature alone expresses binding consent. For most multilateral treaties, signature is subject to ratification: it authenticates the text and creates an obligation of good faith (not to defeat the treaty's object and purpose) but does not bind.
Ratification: The formal act by which a state confirms its consent to be bound, following domestic constitutional processes. Ratification is the primary mode for multilateral treaties. The VCLT requires ratification to be communicated to the other parties or the depositary.
Accession: A state that did not participate in the negotiation of a treaty may later join it through accession, if the treaty so permits. Accession has the same legal effect as ratification.
Approval or acceptance: Functionally equivalent to ratification in VCLT usage, employed by some states for executive agreements not requiring parliamentary ratification.
📋 Facts: Germany had signed but never ratified the 1958 Geneva Convention on the Continental Shelf. Denmark and the Netherlands argued Germany was nonetheless bound by its equidistance rule.
⚖️ Issue: Whether a signatory that has not ratified a convention is bound by its provisions as treaty law.
🏛️ Held: It is not. Signature subject to ratification does not create binding treaty obligation; only ratification does. Germany could be bound only if the rule existed independently as custom, which the Court found it did not.
🎯 Principle: For treaty law: consent to be bound is expressed by ratification, not mere signature. A non-ratifying signatory owes at most the Article 18 obligation not to defeat the treaty’s object and purpose.
🔗 Full case notes
S ignature (binding or subject to ratification)
R atification: primary mode for multilateral treaties
A ccession: joining after negotiation closed
A pproval or acceptance: functionally equivalent to ratification
Reservations
A reservation is a unilateral statement made by a state when signing, ratifying, or acceding to a treaty, whereby it purports to exclude or modify the legal effect of certain provisions of the treaty in their application to that state.
This definition from Article 2(1)(d) VCLT identifies the core function of a reservation: it allows a state to participate in a multilateral treaty while carving out specific obligations it is unwilling to accept. Without reservations, states face a binary choice: accept the treaty in full or not at all. Reservations make multilateral treaty-making politically viable by allowing partial adherence.
Validity of Reservations
Article 19 VCLT: a reservation is valid unless it is prohibited by the treaty, the treaty provides only specific reservations (and this is not among them), or the reservation is incompatible with the object and purpose of the treaty.
The object and purpose test is the most important limit. A reservation that strikes at the core obligation of the treaty is invalid. The ICJ applied this test in its Advisory Opinion on Reservations to the Genocide Convention (1951).
📋 Facts: Several states made reservations to the Genocide Convention (1948). Other states objected. The question arose whether a state making reservations incompatible with the Convention's object and purpose could still be a party, and whether objecting states could treat the reserving state as not a party.
⚖️ Issue: What is the rule governing the validity and effect of reservations to a multilateral treaty?
🏛️ Held: The ICJ held that a state may make a reservation even if other parties object, provided the reservation is compatible with the object and purpose of the treaty. If incompatible, the reserving state cannot be considered a party. A state objecting to a reservation may treat the reserving state as not a party to the Convention as between them.
🎯 Principle: The object and purpose test for reservation validity. A reservation incompatible with the treaty's core purpose is invalid. This Advisory Opinion shaped Articles 19 to 23 VCLT.
🔗 Full case notes
Effect of Reservations on Treaty Relations
Articles 20 to 23 VCLT govern the effect of reservations on the bilateral treaty relationship between states.
Acceptance of a reservation by another party makes the reserving state a party to the treaty in relation to that accepting state. The reserved provision is modified to the extent of the reservation in the bilateral relationship between them.
Objection to a reservation by another party does not necessarily prevent the treaty from entering into force between them: the objecting state may allow the treaty to operate while excluding the provision affected by the reservation, unless it declares that no treaty relationship exists.
The reservation system creates a network of bilateral modified obligations within the framework of a single multilateral treaty. Different pairs of states may have different obligations under the same treaty.
| Dimension | Reservation | Interpretive Declaration |
|---|---|---|
| Purpose | Exclude or modify legal effect of a provision | State how the declaring state understands a provision |
| Legal effect | Modifies treaty obligations | No modification: purely declaratory |
| Validity test | Object and purpose test (Article 19 VCLT) | Not subject to reservation rules |
| Strategic use | Limit binding obligations | Preserve flexibility without triggering objection rules |
Termination of Treaties
A treaty may terminate in seven ways under the VCLT.
By Consent of the Parties
Article 54 VCLT: a treaty may be terminated at any time by consent of all the parties, following the same procedure used for its conclusion. A bilateral treaty terminates when both parties agree. A multilateral treaty terminates when all parties consent or when the treaty itself specifies a termination procedure.
By Treaty Provision
Most treaties contain provisions for their own termination: a fixed term, a withdrawal clause, or a denunciation provision. Article 56 VCLT: where a treaty contains no provision for termination or withdrawal, it cannot be denounced unless it is established that the parties intended to admit the possibility of denunciation, or unless a right of denunciation may be implied by the nature of the treaty.
Material Breach
Article 60 VCLT: a material breach of a bilateral treaty by one party entitles the other to invoke the breach as a ground for terminating or suspending the treaty.
For multilateral treaties, the rules are more complex: a material breach entitles the other parties by unanimous agreement to suspend or terminate the treaty in whole or in part in relations with the defaulting state, or any party specially affected by the breach to suspend the treaty in relations between itself and the defaulting state.
A material breach is defined as a repudiation of the treaty not sanctioned by the VCLT, or the violation of a provision essential to the accomplishment of the object and purpose of the treaty.
Supervening Impossibility of Performance
Article 61 VCLT: a party may invoke impossibility of performance as a ground for terminating a treaty if the impossibility results from the permanent disappearance or destruction of an object indispensable for the execution of the treaty.
If a river that formed the basis of a boundary treaty permanently dries up, performance becomes impossible. The impossibility must be permanent: temporary impossibility entitles only suspension, not termination. A state that contributed to the impossibility through its own breach cannot invoke Article 61.
Fundamental Change of Circumstances (Rebus Sic Stantibus)
Article 62 VCLT codifies the doctrine of rebus sic stantibus: a fundamental change of circumstances may be invoked as a ground for terminating or withdrawing from a treaty.
The conditions are strict. The change must relate to circumstances existing at the time of the treaty's conclusion. It must be fundamental, not merely significant. The circumstances must have constituted an essential basis of the consent of the parties. The effect of the change must radically transform the extent of obligations remaining to be performed.
The ICJ has consistently interpreted Article 62 narrowly. In the Gabcikovo-Nagymaros Case (1997), Hungary invoked rebus sic stantibus to justify abandoning a dam project treaty with Czechoslovakia (now Slovakia). The ICJ rejected the plea: political and economic changes, while significant, did not radically transform Hungary's obligations under the treaty.
📋 Facts: Hungary and Czechoslovakia concluded a treaty in 1977 to build a dam system on the Danube. Hungary later suspended and abandoned its part of the project, invoking changed circumstances (political transformation, environmental concerns) and ecological necessity.
⚖️ Issue: Whether Hungary was entitled to terminate or suspend the treaty under Articles 61 and 62 VCLT.
🏛️ Held: The ICJ rejected both grounds. Changed political and economic circumstances did not radically transform Hungary's obligations. Environmental concerns were legitimate but could be addressed through treaty renegotiation, not unilateral termination. The necessity defence also failed.
🎯 Principle: Rebus sic stantibus is a narrow doctrine. Political and social changes since treaty conclusion do not automatically justify termination. The test is whether the change radically transforms the obligations, not merely makes them harder or less desirable.
🔗 Full case notes
Jus Cogens and Conflict
Article 53 VCLT: a treaty that conflicts with a peremptory norm (jus cogens) is void ab initio. Article 64: if a new jus cogens norm emerges after a treaty's conclusion, the treaty becomes void.
Effect of War on Treaties
The VCLT does not address the effect of war on treaties, leaving this to customary law. The general rules are: bilateral treaties between belligerent states are suspended or terminated on the outbreak of war. Multilateral treaties continue to bind neutral states. Treaties specifically designed to operate in wartime (Geneva Conventions, Hague Conventions) are activated, not terminated, by armed conflict.
C onsent of all parties
B y treaty provision (withdrawal clause)
S upervening impossibility (Article 61)
I ntermediary breach: material breach (Article 60)
R ebus sic stantibus: fundamental change (Article 62)
J us cogens: new peremptory norm (Article 64)
W ar: customary rules (not in VCLT)
Common Confusions
Article 62 is deliberately narrow and the ICJ applies it restrictively. Political change, economic difficulty, and changed preferences do not qualify. The change must fundamentally transform the obligations themselves, not merely the desirability of performance. Gabcikovo confirms that inconvenience is not grounds for termination.
A reservation only modifies the bilateral relationship between the reserving state and states that accept the reservation. It has no effect on relations between non-reserving parties. The multilateral treaty continues intact between states that have made no reservations.
For most multilateral treaties, signature subject to ratification does not create binding obligation. It authenticates the text and creates only an obligation not to defeat the treaty's object and purpose (Article 18 VCLT). Binding obligation arises only upon ratification, accession, or approval.
Key Takeaways
Formation: five stages: negotiation, adoption, authentication, consent, entry into force.
Consent modes: SRAA: signature, ratification, accession, approval.
Reservations: exclude or modify effect of provisions. Validity test: compatible with object and purpose (Article 19). Genocide Convention Advisory Opinion (1951). Bilateral modification within multilateral framework.
Termination: CBSIRJW: consent, treaty provision (by withdrawal clause), supervening impossibility, material breach, rebus sic stantibus, jus cogens, war.
Rebus sic stantibus: narrow. Gabcikovo: political and economic change insufficient.
Memory Hooks: SRAA: consent modes CBSIRJW: termination modes Reservation vs interpretive declaration table
Reservation to a Treaty
A reservation is a unilateral statement made by a state when signing, ratifying, or acceding to a treaty, by which it purports to exclude or modify the legal effect of certain provisions of the treaty in their application to that state (Article 2(1)(d) VCLT).
The validity of a reservation is governed by Article 19 VCLT. A reservation is valid unless it is prohibited by the treaty, the treaty provides only specified reservations and this is not among them, or the reservation is incompatible with the object and purpose of the treaty. The ICJ developed this test in its Advisory Opinion on Reservations to the Genocide Convention (1951), holding that a reservation incompatible with a treaty's core purpose cannot be accepted.
The effect of a reservation is bilateral: it modifies the treaty relationship only between the reserving state and states that accept the reservation. States that object to the reservation may exclude the affected provision while maintaining the treaty relationship, or may treat the reserving state as not a party at all. The result is a network of modified bilateral obligations within the single multilateral framework.
Part B (15 marks)
Discuss the Formation, Reservations and Termination of Treaties under the Vienna Convention on the Law of Treaties, 1969
- VCLT 1969: codification of customary law on treaties; in force 1980; near universal acceptance
- Treaty definition Article 2(1)(a): international agreement between states in written form governed by international law
- Five stages of formation: Negotiation, Adoption (Article 9), Authentication, Consent (SRAA), Entry into Force
- SRAA consent modes: Signature, Ratification, Accession, Acceptance/Approval (Articles 11-16)
- Reservations Article 19: must be compatible with object and purpose (Genocide Convention Opinion 1951)
- Pacta sunt servanda Article 26: every treaty in force is binding and must be performed in good faith
- Termination modes CBSIRJW: Consent, By treaty provision, Supervening impossibility, materIal breach, Rebus sic stantibus, Jus cogens, War
- Article 60: material breach; Article 62: fundamental change; Article 64: emergence of new jus cogens