What a Treaty Is, and Its Kinds

An agreement. There must be a meeting of wills. A unilateral declaration is not a treaty, though it may bind, as the Ihlen declaration in [Acquisition of State Territory] shows.

Between States. For the purposes of this Convention.

In written form. For the purposes of this Convention, and article 3 preserves the validity of oral agreements outside it.

Governed by international law. This is the element that does the real work. A contract between two States for the purchase of a building, expressed to be governed by the law of the place where the building stands, is not a treaty. What makes an instrument a treaty is the intention to create obligations under international law.

Whatever its particular designation. The name is irrelevant. Convention, covenant, charter, statute, protocol, pact, agreement, exchange of notes, memorandum, declaration, act, concordat, modus vivendi: all of them are treaties if the definition is satisfied, and none of them is a treaty if it is not.

The other definitions in article 2 are worth knowing because the later articles use them: ratification, acceptance, approval and accession each mean the international act by which a State establishes on the international plane its consent to be bound; full powers means a document designating a person to represent the State; a reservation means 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 in their application to that State; negotiating State, contracting State, party, third State and international organization are all defined there too.

The kinds of treaty

Three classifications recur, and MU asks for kinds by name.

By the number of parties

Bilateral, between two States. Multilateral, among many. The distinction matters for reservations, which arise chiefly in multilateral treaties, and for the effect of a breach, dealt with in [Termination and Suspension of Treaties].

By function

The classification met in [Treaties as a Source] and the one worth most marks.

Law-making treaties, or traites-lois, laying down general rules of conduct for many States. The Charter, the Convention on the Law of the Sea, this Convention itself, the Geneva Conventions.

Treaty contracts, or traites-contrats, settling a particular matter between two or a few States: a boundary, an extradition arrangement, an air services agreement, a loan.

Why it matters. Only a law-making treaty contains a rule capable of general application, so only a law-making treaty is a realistic candidate to pass into custom and bind non-parties on the North Sea conditions. A boundary treaty will never become a rule for anybody else.

By what is required to conclude them

Treaties in simplified form, concluded by signature alone or by an exchange of notes, with no ratification. Formal treaties, requiring signature followed by ratification.

That distinction decides the practical question in [Making a Treaty: From Full Powers to Entry Into Force]: at what moment is the State bound?

What is not a treaty

The most valuable half of the topic, because the errors are here.

A memorandum of understanding intended to be political. Many instruments between States are deliberately drafted to avoid legal obligation, using "will" rather than "shall", "participants" rather than "parties", and omitting entry into force and dispute settlement clauses. Whether such an instrument is a treaty is decided by the intention to create obligations under international law, judged objectively from the terms and the circumstances, and not by its title.

A contract governed by municipal law, even between two States.

A unilateral declaration. It may bind the declaring State in good faith, and Eastern Greenland is the classic instance, but it is not an agreement.

A resolution of an international organisation. Even one adopted unanimously and drafted in normative language: [Resolutions of the General Assembly] explains why.

An agreement between a State and a foreign company. The parties are not both States, and the agreement is generally governed by some municipal law or by the terms of an investment treaty, as [Treatment of Aliens and Diplomatic Protection] sets out.

India and the Vienna Convention

India has not ratified the Vienna Convention on the Law of Treaties. That fact must be stated correctly and it changes less than it appears to.

Most of the Convention is declaratory of custom, so its rules bind India as custom. The accurate form in an answer is that the rule binds India as customary international law and the Convention states it, not that the Convention binds India.

Where the Convention is progressive development rather than codification, chiefly parts of the invalidity and termination provisions and the procedural articles, the position for India is the customary rule, which may be less precise.

A worked example

State WW and State XX sign four instruments in a week. First, a document called a Memorandum of Understanding on Cultural Cooperation, saying the participants "will endeavour" to exchange scholars and containing no entry into force clause. Second, an exchange of notes agreeing that each will admit the other's diplomatic bags without inspection. Third, a contract by which State WW buys a building in State XX's capital, expressed to be governed by State XX's law. Fourth, a Declaration by State WW's foreign minister that it will not test weapons in the atmosphere.

The Memorandum. Probably not a treaty. The test is the intention to create obligations under international law, and "will endeavour", "participants" and the absence of an entry into force clause point away from it. Its title is irrelevant either way, since article 2(1)(a) applies whatever the particular designation.

The exchange of notes. A treaty. Article 2(1)(a) covers an agreement embodied in two or more related instruments, and article 13 provides for consent to be bound expressed by an exchange of instruments constituting a treaty.

The building contract. Not a treaty. It is an agreement between States, in writing, but it is governed by State XX's municipal law and not by international law, and that element is what the definition turns on.

The Declaration. Not a treaty, because there is no agreement. It may nevertheless bind State WW: a unilateral declaration made publicly and with intent to be bound can create an obligation, which is what Eastern Greenland decided about the Ihlen declaration.

Change one fact: the Memorandum is oral. Then it falls outside the Convention entirely under article 2(1)(a), and article 3 preserves the position: the absence of writing does not affect the legal force of the agreement, and the customary rules apply to it.

Distinctions table

What it does NOT mean

The name decides nothing. Article 2(1)(a) says whatever its particular designation.

An oral agreement is not void. It falls outside the Convention and article 3 preserves its legal force and the application of customary rules.

Not every written agreement between States is a treaty. It must be governed by international law and intended to create obligations under it.

The Convention is not retrospective. Article 4 applies it only to treaties concluded after its entry into force for the States concerned, without prejudice to rules that bind independently of it.

India is not a party, and is bound by most of the same rules as custom.

Limits and criticism

The definition excludes agreements it ought to cover. By limiting itself to treaties between States in written form, the Convention leaves out agreements with international organisations, which needed a separate convention in 1986, and oral agreements, which are left to a custom that the Convention itself is the best evidence of.

Intention is easy to state and hard to find. Whether an instrument was meant to create legal obligations is decided from its terms and circumstances, and States increasingly draft to leave the question open on purpose, so the volume of instruments of uncertain status grows.

The law-making and contract classification is descriptive. No rule in the Convention turns on it. Its value is in explaining which treaties can generate custom, and a candidate who states it without that explanation has stated a taxonomy rather than a rule.

Quick revision

Article 2(1)(a): a treaty is an international agreement concluded between States in written form and governed by international law, whether in one instrument or more, and whatever its particular designation.

Essentials: an agreement; between States; in writing; governed by international law, meaning intended to create obligations under it.

Article 1 applies the Convention to treaties between States. Article 3 preserves the force of agreements outside it, including oral ones. Article 4: not retrospective. Article 5: applies to constituent instruments of organisations. Article 6: every State has capacity.

Kinds: bilateral and multilateral; law-making (traites-lois) and treaty contracts (traites-contrats), only the first being a candidate to pass into custom; simplified form and formal, the difference being ratification.

Not treaties: a political memorandum of understanding; a contract governed by municipal law; a unilateral declaration; a resolution of an organisation; an agreement between a State and a company.

India has not ratified the Convention and is bound by most of its content as custom.

Test yourself

1. Define a treaty and identify the element that does the most work.

Article 2(1)(a) of the Vienna Convention 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. The element that decides most real cases is that it be governed by international law, which means the parties intended to create obligations under international law rather than under some municipal law or none at all. A written agreement between two States for the sale of a building, expressed to be governed by one State's own law, satisfies every element except that one and is not a treaty.

2. Does the name of an instrument matter?

No. Article 2(1)(a) applies whatever its particular designation, so convention, covenant, charter, statute, protocol, pact, agreement, exchange of notes, declaration, act, concordat and modus vivendi are all treaties if the definition is satisfied and none of them is a treaty if it is not. The practical consequence is that an instrument called a Memorandum of Understanding may be a treaty, and an instrument called a Convention may not be if it was not intended to create legal obligations.

3. Is an oral agreement between States binding?

It may well be, and the Convention says so obliquely. Article 2(1)(a) confines the Convention to agreements in written form, and article 3 then provides that the fact that the Convention does not apply to agreements not in written form does not affect their legal force, or the application to them of any rules set out in the Convention to which they would be subject under international law independently of it. So an oral agreement is a treaty at customary law and most of the Convention's content applies to it as custom.

4. Distinguish law-making treaties from treaty contracts, and say why it matters.

A law-making treaty lays down general rules of conduct for a large number of States, such as the Charter, the Convention on the Law of the Sea or the Vienna Convention itself. A treaty contract settles a particular matter between two or a few States, such as a boundary, an extradition arrangement or a loan. The distinction matters because only a law-making treaty contains a rule capable of general application, and so only a law-making treaty is a realistic candidate to pass into customary international law and bind non-parties on the conditions set out in the North Sea Continental Shelf cases.

5. India has not ratified the Vienna Convention. Is India bound by its rules?

By most of them, as customary international law rather than as treaty. Much of the Convention is declaratory of custom, including pacta sunt servanda in article 26, the rule in article 27 that internal law is no justification for non-performance, and the interpretation rules in articles 31 to 33. Those bind India as custom, and the Convention is the best statement of their content. Where the Convention is progressive development rather than codification, particularly parts of the invalidity and termination provisions and the procedural articles, India is governed by the customary rule, which may be less precise. The accurate form of words is that the rule binds India as custom and the Convention states it.

6. How do you tell a treaty from a political memorandum of understanding?

By whether the parties intended to create obligations under international law, judged objectively from the terms of the instrument and the circumstances of its conclusion, and not by its title, which article 2(1)(a) makes irrelevant. The pointers are linguistic and structural: shall against will, parties against participants, enters into force against comes into effect, and the presence or absence of provisions on entry into force, registration, dispute settlement and termination. States increasingly draft deliberately to leave the question open, which is why instruments of uncertain status have multiplied.