The Law of Treaties under International Law
The Law of Treaties under International Law
1. Introduction
The Law of Treaties is a core component of Public International Law, governing the creation, interpretation, and enforcement of agreements (treaties) between sovereign states and international organizations.
The primary source is the Vienna Convention on the Law of Treaties (VCLT) 1969, often described as the "treaty on treaties." It codifies customary international law and applies to written treaties between states.
2. Definition of a Treaty
Article 2(1)(a) of the VCLT 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."
Treaties can be called:
Conventions
Accords
Agreements
Protocols
Charters
3. Key Elements of Treaty Law
A. Treaty Formation
The formation of a treaty involves:
Negotiation
Adoption of the text
Authentication
Consent to be bound (through signature, ratification, accession, etc.)
Entry into force
Case: Qatar v. Bahrain (Jurisdiction and Admissibility), ICJ 1994
The ICJ held that a series of exchanges between Qatar and Bahrain amounted to a legally binding agreement, even though it wasn’t called a “treaty.”
B. Consent to be Bound
Under Article 11–17 VCLT, states may express consent to be bound by:
Signature
Ratification
Acceptance or Approval
Accession
Case: Maritime Delimitation and Territorial Questions (Qatar v. Bahrain)
ICJ affirmed that even minutes of meetings and mutual statements could establish binding commitments, showing that formality is less important than intent.
C. Pacta Sunt Servanda (Article 26 VCLT)
Means: “Agreements must be kept.”
A treaty in force is binding upon the parties and must be performed in good faith.
Case: Namibia Advisory Opinion (1971)
The ICJ emphasized the binding nature of treaties and the duty to perform them in good faith under Article 26.
D. Invalidity of Treaties (Articles 46–53 VCLT)
A treaty may be invalid if:
It violates domestic law of fundamental importance (Art. 46)
There was error, fraud, corruption, or coercion
It conflicts with a peremptory norm of international law (jus cogens)
Case: Armed Activities on the Territory of the Congo (DRC v. Rwanda)
Rwanda argued that its withdrawal from certain treaties was valid under the VCLT, but the ICJ reaffirmed the binding nature of obligations unless invalidated under strict conditions.
E. Interpretation of Treaties (Articles 31–33 VCLT)
Article 31: General Rule of Interpretation
Good faith
Ordinary meaning of the terms
In context
In light of object and purpose
Article 32: Supplementary means (preparatory work, circumstances)
Article 33: Treaties authenticated in two or more languages
Case: Kasikili/Sedudu Island (Botswana/Namibia)
The ICJ applied Article 31 to interpret a colonial treaty, emphasizing object, purpose, and ordinary meaning.
F. Termination or Suspension of Treaties
Under Articles 54–64 VCLT, a treaty may be terminated:
By consent
Through a withdrawal clause
Material breach (Art. 60)
Impossibility of performance (Art. 61)
Fundamental change of circumstances (Rebus sic stantibus) – Art. 62
Emergence of new jus cogens norm (Art. 64)
Case: Gabcikovo-Nagymaros Project (Hungary/Slovakia), ICJ 1997
Hungary tried to suspend and terminate a treaty based on ecological concerns and fundamental change. The ICJ rejected most of the arguments, reiterating that termination rules are strict and exceptions narrow.
G. Jus Cogens and Treaties
A treaty is void if it conflicts with a peremptory norm (jus cogens) of international law — norms from which no derogation is permitted (e.g., prohibition of genocide, slavery, torture).
Case: East Timor (Portugal v. Australia), ICJ 1995
Portugal challenged a treaty between Australia and Indonesia affecting East Timor. While not directly invalidated under jus cogens, the case highlighted how third-party rights and norms can affect treaties.
4. Types of Treaties
Bilateral treaties – Between two parties
Multilateral treaties – Between multiple states (e.g., UN Charter)
Constituent treaties – Establish international organizations
5. Treaty vs. Other International Instruments
Not all international instruments are treaties (e.g., MOUs may not be legally binding).
Case: Nuclear Tests Case (Australia v. France; New Zealand v. France), ICJ 1974
France made unilateral declarations to cease atmospheric nuclear tests. The ICJ held that such declarations can create legal obligations, showing that non-treaty instruments may still have legal weight.
6. Conclusion
The Law of Treaties is a structured, codified system grounded in state consent and the rule of law in international relations. The Vienna Convention on the Law of Treaties (1969) remains the cornerstone, providing a balanced framework for:
Creating
Interpreting
Enforcing
Terminating treaties
Cases decided by the International Court of Justice (ICJ) and other tribunals show how these principles are applied in practice, ensuring stability and predictability in international law.
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