Rights and Duties of the Parties, and Third States

The three words that matter are "with respect to that party". A treaty in force since 1970 does not reach back over a State that joined in 2010.

Situations which ceased to exist. The article distinguishes a past act from a continuing situation. A treaty binds a party in respect of a situation continuing after entry into force, which is why a continuing occupation or a continuing detention is not shielded by article 28 merely because it began earlier.

Territorial scope: article 29

Unless a different intention appears from the treaty or is otherwise established, a treaty is binding upon each party in respect of its entire territory.

The presumption is entirety, and it may be displaced, which is why treaties sometimes carry a territorial application clause, and why a federal State cannot ordinarily confine a treaty to some of its units by its own decision.

Successive treaties on the same subject: article 30

Article 30(1). The rules are subject to article 103 of the Charter, under which Charter obligations prevail over obligations under any other international agreement.

Article 30(2). Where a treaty specifies that it is subject to, or not to be considered incompatible with, an earlier or later treaty, that other treaty prevails. So an express compatibility clause decides the question.

Article 30(3), identical parties. Where all the parties to the earlier treaty are also parties to the later one, and the earlier is not terminated or suspended under article 59, the earlier applies only to the extent that its provisions are compatible with the later.

Article 30(4), different parties.

(a) As between States parties to both treaties, the rule in paragraph 3 applies.

(b) As between a State party to both and a State party to only one, the treaty to which both are parties governs their mutual rights and obligations.

Article 30(5) preserves article 41, the questions of termination and suspension under article 60, and any question of responsibility arising for a State from concluding or applying a treaty incompatible with its obligations to another State under another treaty.

Read 30(4)(b) with 30(5) together and the practical answer emerges. A State that promises inconsistent things to two different partners is not relieved by article 30. Each partner may hold it to their own treaty, and the State is responsible for the breach of whichever it fails to perform.

Third States: articles 34 to 38

Article 34, the general rule. A treaty does not create either obligations or rights for a third State without its consent. This is pacta tertiis nec nocent nec prosunt, and it follows from consent as the basis of obligation.

Obligations, article 35

An obligation arises for a third State if the parties intend the provision to be the means of establishing the obligation and the third State expressly accepts that obligation in writing.

Two requirements, both strict: the parties' intention and the third State's express written acceptance. In substance this is a collateral agreement, which is why the burden is set so high.

Rights, article 36

A right arises for a third State if the parties intend the provision to accord that right either to the third State, or to a group of States to which it belongs, or to all States, and the third State assents. Its assent is presumed so long as the contrary is not indicated, unless the treaty otherwise provides.

The asymmetry is deliberate. An obligation needs express written acceptance; a right needs only assent, and assent is presumed. Nothing is imposed on the third State either way, since it may decline.

Article 36(2). A State exercising such a right shall comply with the conditions for its exercise provided in the treaty or established in conformity with it. A third State cannot take the benefit and reject the conditions attached to it.

Revoking, article 37

37(1). An obligation arisen under article 35 may be revoked or modified only with the consent of the parties and of the third State, unless it is established they had otherwise agreed.

37(2). A right arisen under article 36 may not be revoked or modified by the parties if it is established that the right was intended not to be revocable without the third State's consent.

So an obligation, once accepted, is protected absolutely, while a right is protected only if it was intended to be irrevocable.

The bridge to custom, article 38

Nothing in articles 34 to 37 precludes a rule set forth in a treaty from becoming binding upon a third State as a customary rule of international law, recognised as such.

This is the escape from the whole section, and it is the escape that matters most in practice. A non-party is not bound by the treaty; it may be bound by the same rule as custom. The conditions were set out in the North Sea Continental Shelf cases and are worked in [Custom] and [Treaties as a Source]: the provision must be of a fundamentally norm-creating character, and there must be widespread and representative participation together with settled practice and evidence of a belief that the practice is obligatory.

The distinction to keep in an answer. A State is not bound by the Convention on the Law of the Sea if it is not a party. It is bound by those of its rules that have passed into custom, and it is bound by them as custom, so it may not be sued under the Convention's dispute settlement machinery.

Amendment and modification: articles 39 to 41

Article 39. A treaty may be amended by agreement between the parties, and the rules on conclusion in Part II apply to the amending agreement except as the treaty otherwise provides.

Article 40, multilateral treaties. Unless the treaty otherwise provides, any proposal to amend as between all the parties must be notified to all the contracting States, each of which has the right to take part in the decision on what to do about it and in the negotiation and conclusion of the amending agreement. Every State entitled to become a party to the treaty is entitled to become a party to the treaty as amended. Crucially, the amending agreement does not bind any State already a party which does not become a party to it, and article 30(4)(b) governs that State's relations. A State becoming a party after the amendment enters into force is, failing a different intention, a party to the amended treaty, and a party to the unamended treaty in relation to any party not bound by the amendment.

The consequence is the awkward one every amended convention lives with. Two versions of the same treaty operate at once, and which version governs depends on the pair of States concerned.

Article 41, modification between some parties only. Two or more parties may agree to modify the treaty as between themselves alone if the possibility is provided for by the treaty, or if the modification is not prohibited and does not affect the enjoyment by the other parties of their rights or the performance of their obligations, and does not relate to a provision derogation from which is incompatible with the effective execution of the object and purpose of the treaty as a whole. The modifying parties must notify the others of their intention and of the modification.

A worked example

Treaty PP of 1990 binds States AA, BB and CC and requires each to keep a river navigable. Treaty QQ of 2015 binds AA, BB and DD on the same subject and permits damming. State CC never joined QQ. State EE is party to neither, but the rule requiring notification of works on a shared river, stated in article 5 of PP, has been generally accepted in practice as law. State AA dams the river.

AA and BB. Both are parties to PP and QQ. Article 30(4)(a) applies the paragraph 3 rule: PP applies only to the extent compatible with QQ, so as between AA and BB the damming is permitted.

AA and CC. CC is party only to PP. Article 30(4)(b): the treaty to which both are parties governs, so PP governs and AA is in breach as against CC. Article 30(5) preserves the question of responsibility, so AA answers to CC.

AA and DD. Only QQ binds both, so QQ governs.

Can AA plead its new domestic Dams Act? No. Article 27 forbids invoking internal law as justification for failure to perform, subject only to article 46 on invalid consent.

Is EE bound by article 5 of PP? Not as a treaty; article 34 says a treaty creates no obligations or rights for a third State without its consent. But article 38 preserves the possibility that the rule in article 5 binds EE as a customary rule recognised as such, and on these facts it does.

Change one fact: AA and BB agree in 2015 to modify PP between themselves alone. Then article 41 applies, and the agreement is permissible only if PP allows it or, PP not prohibiting it, the modification does not affect CC's enjoyment of its rights or performance of its obligations and does not touch a provision whose derogation is incompatible with the object and purpose of PP as a whole. Damming a river CC relies on would fail the first condition.

Distinctions table

What it does NOT mean

Good faith is not a licence to rewrite. Article 26 requires performance of what was agreed.

Article 27 does not make internal law irrelevant to validity. Article 46 preserves a narrow plea, and article 27 is expressly without prejudice to it.

Article 28 does not shield continuing situations. It excludes acts and facts that took place, and situations that ceased to exist, before entry into force for that party.

Article 30 does not resolve the conflict away. Article 30(5) preserves responsibility, so a State bound inconsistently is liable to whichever partner it fails.

A third State is not bound by a treaty because most States have joined it. It may be bound by the same rule as custom under article 38, which is a different thing with different consequences.

An amendment does not bind existing parties automatically. Article 40(4) is explicit that it does not.

Limits and criticism

Article 30 handles conflicts of treaty obligation by priority rules that assume the conflict is soluble. Where it is not, the Convention offers only the reminder in paragraph 5 that responsibility remains, which tells the State it will be liable to somebody without telling it what to do.

Article 103 of the Charter is preserved but not explained, and how far the primacy of Charter obligations extends, particularly to decisions of the Security Council as distinct from the Charter's own text, is one of the largest unsettled questions in the subject.

Article 38 is doctrinally awkward. It says a treaty rule may bind a non-party as custom, which is true and important, and it gives no guidance at all on when the passage happens, leaving the whole question to the North Sea conditions.

Article 41 depends on notification that is often not given, and the other parties rarely have any means of enforcing the conditions in paragraph 1.

Quick revision

Article 26, pacta sunt servanda: every treaty in force binds the parties and must be performed in good faith.

Article 27: internal law is no justification for failure to perform, without prejudice to article 46.

Article 28: not retroactive for acts, facts or situations that ceased before entry into force for that party. Article 29: binding on the entire territory unless otherwise intended.

Article 30: subject to Charter article 103; express compatibility clause prevails; identical parties, the earlier applies only so far as compatible; different parties, the treaty to which both are parties governs; responsibility preserved.

Article 34: no obligations or rights for a third State without its consent. Article 35: obligation needs intention plus express acceptance in writing. Article 36: right needs intention plus assent, presumed; conditions must be complied with. Article 37: obligation revocable only with everyone's consent; right only if intended revocable. Article 38: the rule may bind a third State as custom.

Article 39: amendment by agreement. Article 40: all contracting States notified and entitled to take part; the amendment does not bind a party that does not join it. Article 41: modification inter se only if permitted, or not prohibited and harmless to the others and to the object and purpose, with notification.

Test yourself

1. State the rule in article 26 and explain what good faith adds.

Article 26 provides that every treaty in force is binding upon the parties to it and must be performed by them in good faith. Good faith adds a requirement beyond literal compliance: a party may not perform in a way that deprives the other of the benefit for which it bargained, and may not exercise a power conferred by the treaty for a purpose other than that for which it was given. The three conditions in the article are each significant, since the treaty must be in force under article 24, it binds only the parties by article 34, and performance must satisfy good faith and not merely the letter.

2. Can a State plead its own constitution as an answer to a claim of breach?

No. Article 27 provides that a party may not invoke the provisions of its internal law as justification for its failure to perform a treaty, and internal law here includes the constitution, statutes, subordinate legislation and the decisions of the State's own courts. The rule is expressly without prejudice to article 46, which is a different matter: a plea that the State's consent to be bound was invalid because it was expressed in manifest violation of a rule of its internal law of fundamental importance concerning competence to conclude treaties. That is a challenge to consent, not an excuse for non-performance, and it is deliberately narrow.

3. How does a treaty create an obligation for a State that is not a party?

Only by satisfying article 35, which requires two things: the parties to the treaty must intend the provision to be the means of establishing the obligation, and the third State must expressly accept that obligation in writing. In substance this creates a collateral agreement, and the requirement of express written acceptance means nothing is imposed on the third State. By article 37(1) such an obligation may then be revoked or modified only with the consent of the parties and of the third State, unless it is established they had otherwise agreed.

4. Contrast the position for rights of third States.

Article 36 requires that the parties intend the provision to accord the right to the third State, or to a group of States to which it belongs, or to all States, and that the third State assent, but its assent is presumed so long as the contrary is not indicated, unless the treaty provides otherwise. The asymmetry with obligations is deliberate: conferring a benefit needs no formality, imposing a burden does. By article 36(2) the State exercising the right must comply with the conditions for its exercise provided for in the treaty, so it cannot take the benefit free of the conditions attached, and by article 37(2) the right may be revoked unless it is established that it was intended not to be revocable without the third State's consent.

5. State AA is party to a 1990 treaty with State CC and to a 2015 treaty with State DD, and the two are incompatible. What governs?

Article 30(4)(b) answers it: as between a State party to both treaties and a State party to only one, the treaty to which both States are parties governs their mutual rights and obligations. So the 1990 treaty governs between AA and CC and the 2015 treaty governs between AA and DD, and AA is bound inconsistently. Article 30(5) preserves any question of responsibility arising for a State from concluding or applying a treaty incompatible with its obligations to another State under another treaty, so AA will be responsible to whichever party it fails to perform for. Article 30 does not dissolve the conflict; it allocates it.

6. Explain article 38 and why it matters.

Article 38 provides that nothing in articles 34 to 37 precludes a rule set forth in a treaty from becoming binding upon a third State as a customary rule of international law, recognised as such. It matters because it is the route by which the content of the great multilateral conventions reaches States that never joined them. The non-party remains outside the treaty, so it is not subject to the treaty's dispute settlement machinery and not entitled to its procedural benefits, but it is bound by those of its rules that have passed into custom on the conditions stated in the North Sea Continental Shelf cases, namely that the provision be of a fundamentally norm-creating character and that there be widespread and representative participation together with settled practice accepted as law.