Treaties as Sources of International Law:

In article 38(1)(a) of the Statute of the International Court of Justice, it is provided that the International Court of Justice, in its resolution of disputes, may rely on conventions as a source of law. The commentaries on the draft articles on the law of treaties, 1966, refers to conventions as a more formal term referring to treaties.

Per article 2(1)(a) of the Vienna Convention on the Law of Treaties (1969), herein VCLT, a treaty is “ 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 .”

According to Shaw (2003, p. 88), treaties are “written agreements whereby the states participating bind themselves legally to act in a particular way or to set up particular relations between themselves.”

Elements of the Definition of a Treaty:

1. An agreement between states : Treaties are usually between two or more sovereign states. To reflect contemporary international law where states are not the only subject of international law, Shaw (2022) defined a treaty as “a binding formal agreement, contract, or other written instrument that establishes obligations between two or more subjects of international law (primarily states and international organizations).” Article 3 of VCLT also acknowledges that there can be international agreements between states and other subjects of international law. However, the Vienna Convention on the Law of Treaties is limited only to international agreements concluded between two or more states.

2. A written agreement: Treaties are in written form. Article 3 of VCLT, however, also provides that the legal force of international agreements not in written form is not affected merely because they are unwritten.

How a State Becomes Party to a Treaty:

Article 6 of the VCLT gives every state the capacity to conclude treaties. States become party to a treaty by consenting to be bound by the treaty. A representative of the state must express the state’s consent to be bound by a treaty. According to article 7(1)(a) of VCLT, a person is deemed to represent the state for the purpose of adopting the text of a treaty if he produces full powers. Article 2(1)(c) of VCLT defines full powers:

a document emanating from the competent authority of a State designating a person or persons to represent the State for negotiating, adopting, or authenticating the text of a treaty, for expressing the consent of the State to be bound by a treaty, or for accomplishing any other act with respect to a treaty.

From state practice, however, it may appear that certain persons are designated by the state to represent it for negotiating and adopting the text of a treaty, and such persons, per article 7(1)(b) of VCLT, may not have to produce full powers (the document).

Other persons not required to produce full powers, per article 7(2) of VCLT, and are considered as representing their states for the purpose of adopting/negotiating/authenticating the text of a treaty are:

(a) Heads of State, Heads of Government and Ministers for Foreign Affairs, for the purpose of performing all acts relating to the conclusion of a treaty;

(b) heads of diplomatic missions, for the purpose of adopting the text of a treaty between the accrediting State and the State to which they are accredited;

(c) representatives accredited by States to an international conference or to an international organization or one of its organs, for the purpose of adopting the text of a treaty in that conference, organization, or organ.

When a person claims to represent a state for the purpose of expressing the state’s consent to be bound, and it is later discovered that such person does not have the authority to express the state’s consent, article 8 of VCLT provides that the adoption of the treaty by the unauthorised person shall be without any legal effect unless it has been confirmed by the state.

Ways of Expressing Consent to be Bound:

According to article 11 of VCLT, “the consent of a State to be bound by a treaty may be expressed by signature, exchange of instruments constituting a treaty, ratification, acceptance, approval or accession, or by any other means if so agreed.”

1. Consent to be Bound Through Signature: Whilst in the past a sovereign could merely commit a country to be part of a treaty just by signing, contemporary recognition that various consultations at the national level would have to be made before a nation becomes a party to an international agreement has led to the weakening of the idea that a signature equals consent to be a party to a treaty. Some treaties, however, and per article 12 of VCLT, may provide that the signing of the treaty by the representative of a state indicates the state’s consent to be bound. Article 12 of VCLT also provides that a state that wishes for its signature to represent consent to be bound may also be bound through signing.

2. Consent to be Bound Through Ratification, Acceptance or Approval: Per article 14 of VCLT , a state expresses consent to be bound through ratification, acceptance, or approval when:

(a) the treaty provides for such consent to be expressed by means of ratification;

(b) it is otherwise established that the negotiating States were agreed that ratification should be required;

(c) the representative of the State has signed the treaty subject to ratification; or

(d) the intention of the State to sign the treaty subject to ratification appears from the full powers of its representative or was expressed during the negotiation.

3. Consent to be Bound through Accession: according to the Draft Articles on the Law of Treaties with commentaries (1966), accession is “the traditional method by which a State, in certain circumstances, becomes a party to a treaty of which it is not a signatory.” Article 15 of VCLT provides that:

The consent of a State to be bound by a treaty is expressed by accession when:

(a) the treaty provides that such consent may be expressed by that State by means of accession;

(b) it is otherwise established that the negotiating States were agreed that such consent may be expressed by that State by means of accession; or

(c) all the parties have subsequently agreed that such consent may be expressed by that State by means of accession.

When a state expresses its consent to be bound through ratification, or acceptance, among others, it must communicate such acceptance or consent back to other relevant bodies (like other states), similar to the requirement that acceptance of an offer must be communicated back to the offeror. Article 16 of VCLT makes provisions for such exchange.

How a State Ceases to be Party to a Treaty:

The consent of a state to be bound by a treaty may be invalidated due to an error, fraud, corruption of the state representative, coercion of a representative of a state, and coercion of a state by the threat or use of force.

1. Error: Article 48(1) of the VCLT provides that the consent of a state to be bound by a treaty may be invalidated if there was an error in assuming that a fact was true or a situation existed at the time of concluding the treaty, and the fact being true or the situation existing was an essential basis of the state’s consent to be bound by the treaty. Essentially, and before a state can rely on an error as grounds for invalidating its consent, the state must not have contributed to the error and should not have been put on notice of a possible error.

2. Fraud: Article 49 of VCLT provides that “if a State has been induced to conclude a treaty by the fraudulent conduct of another negotiating state, the state may invoke the fraud as invalidating its consent to be bound by the treaty.”

3. Corruption of the state representative: Article 50 of VCLT provides that “if the expression of a State’s consent to be bound by a treaty has been procured through the corruption of its representative directly or indirectly by another negotiating State, the State may invoke such corruption as invalidating its consent to be bound by the treaty.”

4. Coercion of a state by the threat or use of force: Article 51 of VCLT provides that “the expression of a State’s consent to be bound by a treaty which has been procured by the coercion of its representative through acts or threats directed against him shall be without any legal effect.”

5. Coercion of a state by the threat or use of force: Article 52 of VCLT provides that “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.”

6. The treaty conflicts with a peremptory norm of general international law, usually known as jus cogens: If a state consents to be bound by a treaty, the consent is invalid if the entire treaty is rendered invalid for conflicting with a peremptory norm of general international law or jus cogens. Article 53 of VCLT defined a peremptory norm of general international law as “a norm accepted and recognized by the international community of States as a whole as a norm from which no derogation is permitted and which can be modified only by a subsequent norm of general international law having the same character.” For example, if a state consents to be bound by a treaty meant to traffic humans, the treaty would be considered to conflict with the jus cogens norm against human trafficking, consequently rendering both the treaty and the consent to be bound invalid. Further, article 64 of VCLT provides that if a peremptory norm of general international law subsequently emerges post the conclusion of a treaty, the treaty shall become invalid.

Consequences of being Bound by a Treaty:

When a state is party to a treaty or expresses its consent to be bound by the treaty, article 26 of VCLT provides that the treaty is binding on the state and it must perform the terms of the treaty in good faith. The Latin maxim pacta sunt servanda, meaning “the agreement must be kept”, is used to depict the primary responsibility of states that are party to a treaty.

In performing the terms of a treaty, and pursuant to article 27 of VCLT, a state bound by a treaty “may not invoke the provisions of its internal law as justification for its failure to perform a treaty.”

Interpretation of Treaties:

To determine what the terms of the treaty are, or what states are expected to do under the treaty, articles 31 to 32 of VCLT provides the following guidelines on interpreting treaties: See article 31 and article 32 of VCLT