Reservations to Treaties

Reservations to Treaties are an important part of the Law of Treaties, particularly in relation to multilateral treaties. A reservation allows a State, subject to the applicable rules, to become a party to a treaty while seeking to exclude or modify the legal effect of particular provisions in their application to that State.

The principal rules concerning reservations are contained in Articles 19–23 of the Vienna Convention on the Law of Treaties, 1969 (VCLT).

Meaning of Reservation

Under Article 2(1)(d) VCLT, a reservation is a unilateral statement, however phrased or named, made by a State when signing, ratifying, accepting, approving or acceding to a treaty, whereby it purports to exclude or to modify the legal effect of certain provisions of the treaty in their application to that State.

The important elements are:

• it is a unilateral statement;
• it is made by a State;
• it is made at specified stages of treaty participation;
• it seeks to exclude or modify the legal effect of certain treaty provisions;
• it relates to the application of those provisions to the reserving State.

Purpose of Reservations

Reservations provide flexibility in multilateral treaty-making.

A State may agree with the general objectives of a treaty but disagree with a particular provision.

Instead of:

Accept entire treaty

or

Reject entire treaty

the reservation mechanism may allow:

Accept treaty + exclude/modify specified provision

This encourages wider participation in multilateral treaties.

Example

Suppose a multilateral treaty contains:

Article X → State must follow a particular procedure

State A agrees with the treaty generally but does not wish Article X to apply fully to it.

State A may formulate a reservation to Article X, provided that the reservation is permissible under the treaty and International Law.

When Can a Reservation Be Made?

A reservation may be made when a State:

• signs a treaty;
• ratifies a treaty;
• accepts a treaty;
• approves a treaty;
• accedes to a treaty.

This is expressly reflected in Article 2(1)(d) VCLT.

Reservations and Bilateral Treaties

Reservations are primarily significant in multilateral treaties.

In a bilateral treaty, a proposed reservation would generally operate more like a proposal to modify the agreed terms between the two States rather than a traditional reservation in the multilateral sense.

The reservation regime is therefore particularly important for multilateral conventions.

Article 19: Formulation of Reservations

Article 19 VCLT establishes when a State may formulate a reservation.

A State may formulate a reservation unless:

Treaty Prohibits Reservations

If the treaty expressly prohibits reservations, a State cannot formulate one.

Treaty Permits Only Specified Reservations

If the treaty permits only particular reservations, a State cannot formulate a reservation outside those permitted categories.

Incompatibility with Object and Purpose

A State cannot formulate a reservation that is incompatible with the object and purpose of the treaty.

This is one of the most important limitations on reservations.

Object and Purpose Test

The object and purpose test asks whether the reservation is compatible with the fundamental purpose and essential character of the treaty.

Therefore:

Reservation

↓

Examine treaty

↓

Is reservation prohibited?

↓

Is it outside permitted categories?

↓

Is it incompatible with object and purpose?

↓

If yes → reservation is impermissible

Reservations to the Genocide Convention, 1951

The leading authority is the ICJ’s Advisory Opinion on Reservations to the Convention on the Prevention and Punishment of the Crime of Genocide, 1951.

The Court considered whether a State could make reservations to the Genocide Convention and developed the importance of compatibility with the object and purpose of the treaty.

The opinion significantly influenced the modern law of reservations and the approach later reflected in the VCLT.

Acceptance of a Reservation

Under Article 20 VCLT, the legal effect of a reservation depends partly upon acceptance or objection by other States.

Where a reservation is expressly authorised by the treaty, it may not require subsequent acceptance unless the treaty so provides.

In other circumstances, acceptance by another contracting State may be relevant to the establishment of treaty relations.

Unanimous Acceptance

Where it appears from the limited number of negotiating States and the object and purpose of the treaty that its application in its entirety between all parties is an essential condition of the consent of each one to be bound, a reservation requires acceptance by all parties.

This is particularly relevant where the treaty is based upon complete reciprocity among a small number of States.

Acceptance by an International Organisation

Where the constituent instrument of an international organisation provides otherwise, different rules may apply.

The VCLT therefore recognises particular circumstances in which the consent of a competent organ of an international organisation may be relevant to acceptance of a reservation.

Objection to a Reservation

A State may object to a reservation formulated by another State.

An objection does not necessarily have the same effect in every case.

The objecting State may:

• accept treaty relations with the reserving State while rejecting the reservation; or
• indicate that it does not intend the treaty to enter into force between itself and the reserving State.

The legal consequences depend upon the objection and the applicable VCLT rules.

Legal Effect of Acceptance

Where a State accepts a reservation made by another State, the reserved provision operates between them subject to the reservation.

The reservation therefore modifies the treaty relationship between the relevant States.

Legal Effect of Objection

An objection may prevent the reserved provision from applying between the objecting and reserving States to the extent established by the applicable rules.

An objection does not automatically mean that the entire treaty relationship between the two States disappears.

The precise effect depends upon the terms and intention of the objecting State.

Article 21: Effects of Reservations and Objections

Article 21 VCLT establishes the legal effects of reservations and objections.

Where a reservation is established with regard to another party, the relevant provision is modified for the reserving State in its relations with that party to the extent of the reservation.

Where an objection does not preclude entry into force between the reserving and objecting States, the provisions to which the reservation relates do not apply between them to the extent of the reservation.

Withdrawal of Reservations

A State may generally withdraw a reservation unless the treaty provides otherwise.

Under Article 22 VCLT, withdrawal of a reservation generally does not require the consent of a State that has accepted the reservation.

Similarly, an objection to a reservation may be withdrawn unless otherwise provided.

Withdrawal of Objection

A State that has objected to a reservation may subsequently withdraw its objection.

The withdrawal must comply with the applicable VCLT requirements.

Procedure for Reservations

Article 23 VCLT establishes procedural requirements.

A reservation, express acceptance of a reservation and objection to a reservation must generally be:

• formulated in writing;
• communicated to the contracting States and other States entitled to become parties.

Reservation vs Interpretative Declaration

A reservation seeks to exclude or modify the legal effect of treaty provisions.

An interpretative declaration generally explains how a State understands or interprets a treaty provision without necessarily seeking to alter its legal effect.

Therefore:

Reservation → modifies/excludes legal effect

Interpretative declaration → explains interpretation

However, the label given by a State is not necessarily decisive. The substance and intended legal effect of the statement matter.

Reservation vs Amendment

A reservation is different from an amendment.

Reservation

Operates primarily in the treaty relationship involving the reserving State.

Amendment

Changes the treaty text or its legal framework according to the applicable amendment procedure.

Therefore:

Reservation → modifies application to reserving State

Amendment → changes treaty provisions according to amendment rules

Reservation vs Modification

A reservation does not necessarily modify the treaty for all States.

Its effect is generally limited to the treaty relationship involving the reserving State and other relevant parties.

Reservations and Human Rights Treaties

Reservations have generated significant legal discussion in relation to human-rights treaties.

The issue is particularly important because human-rights treaties may establish obligations designed to protect individuals rather than merely reciprocal State interests.

The validity and effect of reservations therefore require careful examination under:

• the treaty itself;
• the VCLT;
• relevant international practice;
• applicable international jurisprudence.

Invalid Reservations

A reservation may be legally problematic if it:

• is expressly prohibited;
• falls outside permitted categories;
• is incompatible with the treaty’s object and purpose.

The consequences of an impermissible reservation can be complex and may depend upon:

• the treaty;
• the intention of the reserving State;
• the reactions of other States;
• relevant international legal rules.

Reservation and Treaty Participation

A State may use reservations to balance:

National interests

with

Participation in multilateral treaty regimes

For example:

State disagrees with one provision

↓

Formulates permissible reservation

↓

Joins wider treaty regime

This flexibility is one of the principal reasons reservations are important in multilateral treaty law.

Reservations and Pacta Sunt Servanda

Once a valid reservation has been established within the treaty relationship, the treaty continues to bind the parties subject to the legal effect of that reservation.

The principle of pacta sunt servanda under Article 26 VCLT therefore continues to apply to the treaty obligations that remain binding.

Reservations and State Consent

Reservations are closely connected with the principle of State consent.

A State may be unwilling to accept particular treaty provisions in their full form.

The reservation mechanism allows the State to express consent to the treaty while limiting its obligations in a legally recognised manner.

Important VCLT Provisions

Article	Subject
Article 2(1)(d)	Definition of reservation
Article 19	Formulation of reservations
Article 20	Acceptance of and objection to reservations
Article 21	Legal effects of reservations and objections
Article 22	Withdrawal of reservations and objections
Article 23	Procedure regarding reservations
Article 24	Entry into force
Article 26	Pacta sunt servanda

Important Cases

Reservations to the Genocide Convention, 1951

This is the leading authority on treaty reservations.

The ICJ recognised the importance of determining whether a reservation is compatible with the object and purpose of the treaty.

Belilos v. Switzerland, 1988

The European Court of Human Rights examined a purported reservation to the European Convention on Human Rights and considered whether the statement complied with the applicable requirements.

The case demonstrates the importance of examining the substance and legal effect of a purported reservation.

Loizidou v. Turkey, 1995

The European Court of Human Rights considered the validity and effect of a purported reservation concerning the Convention’s jurisdictional provisions.

The case is important in the context of reservations to human-rights treaties.

Reservation Process

The process can be simplified as:

State decides to join treaty

↓

State formulates reservation

↓

Reservation communicated in writing

↓

Other States consider reservation

↓

Acceptance or objection

↓

Determine legal effect

↓

Treaty relationship operates subject to valid reservation

Exam Flowchart

Reservation formulated

↓

Article 19

↓

Is reservation prohibited?

OR

Is it outside permitted reservations?

OR

Is it incompatible with object and purpose?

↓

If yes → impermissible

↓

If permissible → acceptance/objection under Article 20

↓

Legal effect under Article 21

↓

Withdrawal governed by Article 22

↓

Procedure governed by Article 23

Quick Revision

• Reservation → unilateral statement seeking to exclude or modify the legal effect of particular treaty provisions.
• Article 2(1)(d) VCLT → definition.
• Reservations are particularly important in multilateral treaties.
• A reservation may be made when:
  • signing;
  • ratifying;
  • accepting;
  • approving;
  • acceding.
• Article 19 → formulation of reservations.
• A reservation is impermissible if:
  • the treaty prohibits it;
  • it falls outside specifically permitted reservations;
  • it is incompatible with the treaty’s object and purpose.
• Article 20 → acceptance and objection.
• Article 21 → legal effects.
• Article 22 → withdrawal.
• Article 23 → procedure.
• Reservation ≠ interpretative declaration.
• Reservation ≠ amendment.
• The leading case is Reservations to the Genocide Convention (1951).
• Belilos v Switzerland (1988) → reservations and human-rights treaties.
• Loizidou v Turkey (1995) → reservations to human-rights treaties.
• The key test is:

A reservation must not be prohibited by the treaty or incompatible with its object and purpose.

Conclusion

Reservations to Treaties provide an important mechanism for balancing the need for broad participation in multilateral treaties with the particular interests of individual States. Under Article 2(1)(d) of the Vienna Convention on the Law of Treaties, 1969, a reservation is a unilateral statement made by a State when signing, ratifying, accepting, approving or acceding to a treaty, through which it seeks to exclude or modify the legal effect of certain provisions in their application to that State. Article 19 establishes the principal limits on reservations: a reservation is not permitted where the treaty prohibits it, where it falls outside specifically permitted reservations, or where it is incompatible with the object and purpose of the treaty. Articles 20 and 21 regulate acceptance, objections and their legal effects, while Articles 22 and 23 deal with withdrawal and procedural requirements. The modern law of reservations was significantly influenced by the ICJ’s Reservations to the Genocide Convention Advisory Opinion (1951). Reservations are particularly significant in human-rights treaties, where questions may arise concerning whether a reservation undermines the fundamental purpose of the treaty. A reservation must also be distinguished from an interpretative declaration, which ordinarily explains a State’s understanding rather than seeking to alter the legal effect of a provision. Ultimately, the reservation system provides flexibility within multilateral treaty law while ensuring that States cannot use reservations to undermine the fundamental object and purpose of the treaty.