Law of Treaties 1: What is a treaty?

An introduction to the Vienna Convention on the Law of Treaties

The Vienna Convention on the Law of Treaties of 1969 (VCLT) is the main instrument that regulates treaties. It defines a treaty and relates to how treaties are made, amended, interpreted, how they operate and are terminated. It does not aim to create specific substantive rights or obligations for parties – this is left to the specific treaty (i.e. the Vienna Convention on Diplomatic Relations creates rights and obligations for States in their diplomatic relations).

VCLT governs treaties irrespective of its subject matter or objectives – e.g.: treaties to regulate conduct of hostilities (Geneva Conventions on 1949); treaties setting up an international organisation (UN Charter of 1945); and treaties regulating matters between States and other parties on the law of the sea (UN Convention on the Law of the Sea of 1982).

VCLT is a “treaty on treaties”.


What is a treaty?

Article 2(1) (a) of the VCLT defines a treaty as:

“treaty” means 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;

Lets analyse this definition.

(1) International agreement concluded between States governed by international law

The VCLT relates only to treaties concluded between States who are parties to the VCLT, and for treaties that entered into force after the VCLT came into force (The VCLT came into force in 1980. See Article 4 of the VCLT). NB: this does not prevent a provision of the VCLT that reflects customary international law from applying to a treaty even if it does not meet the above requirements. In the Kasikili/Sedudu Island Case the ICJ held that Article 31 of the VCLT on treaty interpretations reflected customary international law and that therefore applied despite the fact that both Botswana and Namibia were not parties to the VCLT and the treaty in question entered into force in 1890. See para 18.

VCLT applied to treaties between States. This does not mean that treaties cannot be concluded between other subjects of international law. As the International Law Commission pointed out in its commentaries, Articles 1, 2 (a) and 3 is not “in anyway intended to deny that other subjects of international law, such as international organisations and insurgent communities, may conclude treaties.”  See Articles 3 and 4 of the VCLT. The latter says:

The present Convention applies to any treaty which is the constituent instrument of an international organization and to any treaty adopted within an international organization without prejudice to any relevant rules of the organization. ✐ Read the Commentary to Article 4. 

  See also Convention on Treaties between States and International Organisations of 1986, which regulated treaties between international organisations themselves and between them and States (for a background on negotiations click here). 

VCLT relates only to treaties that are governed by international law.  There are treaties concluded between States that the national law of

Treaty of Waitangi was signed by the Māori and British Crown in New Zealand in 1840. Remember that the use of the term ‘treaty’ does not itself mean that it comes under the VCLT. See Cameroon vs Nigeria on ‘treaties’ signed with representatives of indigenous peoples during the colonial period giving protectorate or territorial or sovereignty rights to the colonial power.

Treaty of Waitangi was signed by the Māori and British Crown in New Zealand in 1840. Remember that the use of the term ‘treaty’ does not itself mean that it comes under the VCLT. See Cameroon vs Nigeria on ‘treaties’ signed with representatives of indigenous peoples during the colonial period giving protectorate or territorial or sovereignty rights to the colonial power.

one of the parties or by some other national law system chosen by parties regulates, for example, commercial contracts. These are international agreements, but they do not fall within the VCLT. (Dixon speaks of concessionary contracts that could be regarded as “internationalized”). ✐ Read also the Anglo-Iranian Oil Case, ICJ, on developing and exploiting natural resources.

Unlike in domestic law, a treaty does not need reciprocity (consideration) before it becomes a legally binding agreement. ✐ See for example the 1984 Agreement of UK and China on Hong Kong and ICJ’s judgement on the Nuclear Tests Case (see next lesson).

(2) Written agreements embodied in a single instrument or in two or more related instruments 

VCLT relates only to written treaties, whether it is embodied in a single instrument or more than one instrument (for example, exchange of notes are invariably found in two or more instruments). The ILC clarifies that the word “written” does not mean that oral and tacit agreements under international law have no legal force or that the substance of the VCLT articles may not be relevant to them – it merely means that  they are not dealt under the VCLT. Relevant customary law provisions of the VCLT continue to apply to all treaties, regardless of whether it is codified or not. On binding unilateral declarations, see next lesson.

(3) Whatever its particular designation

The law of treaties cover both formal agreements (treaties, convention, protocols, charter, covenant, pact, act, statute) and informal agreements (agreed minutes, exchange of notes or letters, memorandum of understanding).

In  Bangladesh vs Myanmar, ITLOS discussed whether the “agreed minutes” of 1974 was a legally binding agreement within the meaning of Article 15 of UNCLOS. In determining that it was not a legally binding agreement the tribunal considered:

the substance of the minutes – the minutes reflected the fact that “Minutes are a record of the conditional understanding during the course of negotiations and not an agreement within the meaning of Article 15 of the Convention”

the circumstances surrounding the adoption – “From the beginning of the discussions Myanmar made it clear that it did not intend to enter into a separate agreement on the delimitation of the territorial sea and it wanted a comprehensive agreement covering the territorial sea, the exclusive economic zone and the continental shelf”. 

the authority to conclude a legally binding agreement – “the head of the Burmese Delegation was not an official who, in accordance with article 7, paragraph 2, of the Vienna Convention could engage his country without having to produce full powers… no evidence was provided that the Burmese representatives were considered as having the necessary authority to engage the country pursuant to article 7, paragraph 1, of the Vienna Convention.” 

internal acceptance as a treaty – “the fact that the Parties did not submit the 1974 Agreed Minutes to the procedure required by their respective constitutions for binding international agreements is an additional indicator that the Agreed Minutes were not intended to be legally binding.”  How would you reconcile this statement with Article 27 of the VCLT? 

See also the Case Concerning Maritime Delimitation and Territorial Question between Qatar and Bahrain (Qatar vs Bahrain) (Jurisdiction and Admissibility). In this case, the Court held that the 1990 minutes of meeting constituted a legally valid agreement because:

“…international agreements may take a number of forms and  be given a diversity of names”; i.e the fact that this is called “minutes of meeting”, in itself, does not deny it of its character as a treaty under Article 2(1) (a) of the VCLT.

the terms of the agreement and the particular circumstances in which it was drawn up indicates that these minutes do not “…merely give an account of discussions and summarise points of agreement and disagreement. The enumerate commitments to which the parties have consented. Thus they create rights and obligations for parties under international law.”

The intention of the Bahrain Foreign Minister, at the signing of the document, that the minutes are to be considered only a “statement recording a political understanding” and not a legal agreement – is irrelevant.

The fact that the minutes were not registered or registered late, as a treaty, according to Article 102 of the UN Charter does not deprive it of its legal validity.

“Nor is there anything in the material before the Court which would justify deducing from any disregard by Qatar of its constitutional rules relating to the conclusion of treaties that it did not intend to conclude, and did not consider that it had concluded, an instrument of that kind; nor could any such intention, even if shown to exists, prevail over the actual terms of the instrument in question.” ✐ How would this differ from Bangladesh vs Myanmar?

In conclusion, irrespective of what it is called, an instrument will be a treaty if it creates rights and duties that are enforceable under international law. The latter is to be judged based on the nature of the agreement (see next lesson), actual terms of the agreement and the circumstances in which the said agreement was created.


Recommended Reading:

  • VCLT 1969 (click here for the procedural history).
  • Commentaries of the International Law Commission (please note that the numbering and the text of the articles in the final text and the 1966 commentaries can be different). 
  • Official records of the Conference (click here).
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  1. Dear Mam,
    This topic is very useful. thank you for enlighting us. It is greatly appreciated if you can discuss on the interpretation of the treaties as well. I am requesting this for a examination purpose.

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