Pacta Tertiis Nec Nocent Nec Prosunt

Pacta Tertiis Nec Nocent Nec Prosunt is a fundamental principle of the Law of Treaties. It means that a treaty neither imposes obligations upon nor grants rights to a third State without its consent.

The principle is principally reflected in Article 34 of the Vienna Convention on the Law of Treaties, 1969 (VCLT).

The basic rule is:

Treaty between State A + State B

↓

State C = Third State

↓

No treaty obligation or right for State C without consent

Meaning

The Latin maxim pacta tertiis nec nocent nec prosunt can be understood as:

“Agreements neither harm nor benefit third parties.”

In treaty law, it expresses the principle that States that are not parties to a treaty are generally not bound by its obligations and do not acquire rights under it merely because the treaty exists.

It is closely connected with the principle of State consent.

Article 34 VCLT

Article 34 VCLT provides the general rule concerning third States:

“A treaty does not create either obligations or rights for a third State without its consent.”

Therefore:

No consent → No treaty obligation

and ordinarily:

No consent → No treaty right

Who Is a Third State?

A third State is a State that is not a party to the treaty.

For example:

India ↔ State A

↓

Treaty

↓

State B → not a party

↓

State B = Third State

The treaty cannot ordinarily impose obligations upon State B without its consent.

Principle of State Consent

The principle is based on the sovereignty and legal equality of States.

A State cannot ordinarily be bound by an international agreement to which it has not consented.

Thus:

State sovereignty

↓

Requirement of consent

↓

Treaty obligations normally bind only parties

This is an important limitation on the effect of treaties.

Article 35: Obligations for Third States

Although the general rule is that a treaty cannot impose obligations on a third State without its consent, Article 35 VCLT recognises an exception.

An obligation may arise for a third State from a treaty provision if:

• the parties intend the provision to create the obligation; and
• the third State expressly accepts that obligation in writing.

Therefore:

Treaty parties create proposed obligation

↓

Third State expressly accepts in writing

↓

Obligation may arise

Consent is therefore essential.

Article 36: Rights for Third States

A treaty may also create a right for a third State.

Under Article 36 VCLT, a right may arise for a third State where:

• the parties intend the provision to accord the right to the third State; and
• the third State assents.

The third State’s assent is generally presumed where the circumstances do not indicate otherwise.

Therefore:

Treaty parties intend to create right

↓

Third State assents

↓

Third State may acquire treaty right

Difference Between Third-State Obligations and Rights

The VCLT treats obligations and rights differently.

Obligation

Express acceptance in writing is required under Article 35.

Right

The third State’s assent is required under Article 36, and that assent is generally presumed unless the circumstances indicate otherwise.

This distinction is important for examinations.

Article 37: Revocation or Modification

Article 37 VCLT deals with the revocation or modification of obligations or rights arising for third States under Articles 35 and 36.

Obligation

An obligation arising for a third State under Article 35 cannot generally be revoked or modified without the consent of the parties to the treaty and the third State, unless otherwise agreed.

Right

Where a right arises under Article 36, the parties generally cannot revoke or modify that right if it is established that the right was intended not to be revocable or modifiable without the third State’s consent.

Article 38: Customary Rules and Third States

Article 38 VCLT makes an important qualification.

The general rule concerning third States does not prevent a rule contained in a treaty from becoming binding upon a third State as a customary rule of International Law, recognised as such.

Therefore:

Treaty rule

↓

Develops into customary International Law

↓

May bind third States as customary law

But the third State is not bound because of the treaty itself.

It is bound because the rule has independently acquired the status of customary International Law.

Treaty Obligations vs Customary International Law

This distinction is extremely important.

Treaty

State becomes bound through consent to the treaty.

Customary International Law

A State may be bound by a customary rule independently of whether it is party to a particular treaty.

Therefore:

Article 34 does not prevent treaty provisions from becoming customary International Law.

Third States and Multilateral Treaties

The principle is particularly important for multilateral treaties.

For example:

States A, B, C, D → parties to treaty

↓

State E → not a party

↓

State E = third State

↓

Treaty does not ordinarily impose obligations on State E

State E must generally provide the required consent before treaty obligations arise.

Third States and Treaty Rights

A treaty can sometimes provide benefits to a third State.

For example, States A and B could agree:

State A ↔ State B

↓

Treaty creates a benefit for State C

↓

State C may acquire the right if the Article 36 requirements are satisfied

This is sometimes described as a stipulation in favour of a third State.

Third States and Boundary Treaties

Boundary treaties require particular attention.

A boundary arrangement between two States may have consequences for neighbouring States, but such consequences cannot simply be treated as ordinary treaty obligations imposed upon those third States.

The legal position may additionally involve:

• customary International Law;
• recognition;
• acquiescence;
• territorial title;
• other applicable rules.

Therefore, Article 34 must be applied together with the broader law governing territorial relations.

Third States and International Organisations

The general principle concerns third States, but treaties may also involve international organisations.

The 1986 Vienna Convention on the Law of Treaties between States and International Organizations or between International Organizations addresses treaties involving international organisations.

Pacta Sunt Servanda and Pacta Tertiis

These two principles should be studied together.

Pacta Sunt Servanda

Article 26 VCLT

Treaties in force are binding upon their parties and must be performed in good faith.

Pacta Tertiis

Article 34 VCLT

Treaties do not create obligations or rights for third States without their consent.

Thus:

Article 26 → binding force between parties

Article 34 → limitation regarding third States

Exceptions and Qualifications

The principle is important, but it is not absolute in the sense that treaty rules can never have any relevance to third States.

Important qualifications include:

Express Acceptance of Obligation

Under Article 35, a third State may expressly accept an obligation in writing.

Assent to a Treaty Right

Under Article 36, a third State may acquire a right where the relevant conditions are satisfied.

Customary International Law

Under Article 38, a treaty rule may become binding upon a third State as customary International Law.

Other Independent Rules

A treaty may be relevant to a third State where the legal consequence arises from an independent rule of International Law rather than from the treaty itself.

Important Cases

Free Zones of Upper Savoy and the District of Gex, 1932

In Free Zones of Upper Savoy and the District of Gex, the Permanent Court of International Justice considered issues concerning treaties and their effects upon third States.

The case is relevant to the principle that treaties generally operate between their parties and cannot simply impose treaty obligations upon third States.

North Sea Continental Shelf, 1969

The ICJ considered the relationship between treaty provisions and customary International Law.

The case is important for understanding that a treaty provision may have significance for non-parties where the rule independently reflects or develops into customary International Law.

Certain German Interests in Polish Upper Silesia, 1926

The PCIJ considered the effects of international agreements and the relationship between treaty obligations and States not directly bound by the relevant agreement.

Pacta Tertiis vs Pacta Sunt Servanda

Pacta Sunt Servanda	Pacta Tertiis Nec Nocent Nec Prosunt
Agreements must be kept	Treaties do not bind or benefit third States without consent
Article 26 VCLT	Article 34 VCLT
Applies to treaty parties	Protects third States from unwanted treaty effects
Ensures treaty performance	Protects State consent and sovereignty
General rule of treaty performance	General rule concerning third States

Article 34, 35, 36, 37 and 38 Together

These provisions should be remembered as a group:

Article 34

→ General rule: no rights or obligations for third States without consent.

Article 35

→ Obligation for third State requires express written acceptance.

Article 36

→ Right for third State requires assent, generally presumed.

Article 37

→ Revocation or modification of third-State rights and obligations.

Article 38

→ Treaty rules may bind third States as customary International Law.

Quick Revision

• Pacta tertiis nec nocent nec prosunt → treaties neither harm nor benefit third States without consent.
• Article 34 VCLT → general rule.
• A third State is a State that is not a party to the treaty.
• Treaty obligations generally bind only the parties.
• Article 35 → third-State obligation requires:
  • intention of treaty parties;
  • express acceptance by third State;
  • acceptance must be in writing.
• Article 36 → third-State rights may arise where:
  • treaty parties intend to create the right;
  • third State assents.
• Assent to a right is generally presumed unless circumstances indicate otherwise.
• Article 37 → revocation/modification of third-State rights and obligations.
• Article 38 → treaty rules may become customary International Law and bind third States as customary rules.
• Treaty obligations and customary obligations must be distinguished.
• Pacta sunt servanda → Article 26
• Pacta tertiis → Article 34
• North Sea Continental Shelf (1969) → treaty rules and customary International Law.
• The core principle is:

A State cannot ordinarily be bound by a treaty to which it has not consented.

Conclusion

Pacta Tertiis Nec Nocent Nec Prosunt is a fundamental principle of treaty law that protects the sovereignty and consent of States. Under Article 34 of the Vienna Convention on the Law of Treaties, 1969, a treaty does not create obligations or rights for a third State without its consent. The principle means that treaty obligations ordinarily operate only between the parties that have consented to be bound. However, the VCLT recognises important qualifications. Under Article 35, an obligation may arise for a third State where the treaty parties intend to create that obligation and the third State expressly accepts it in writing. Under Article 36, a treaty may create a right for a third State where the parties intend to grant that right and the third State assents, with assent generally presumed unless circumstances indicate otherwise. Article 37 regulates the revocation or modification of such rights and obligations, while Article 38 clarifies that treaty provisions may become binding upon third States as rules of customary International Law. The principle must therefore be distinguished from pacta sunt servanda: Article 26 establishes the binding force of treaties upon their parties, while Article 34 protects non-parties from being bound without consent. The North Sea Continental Shelf Case (1969) is particularly important for understanding the relationship between treaty provisions and customary International Law. Ultimately, the doctrine expresses a basic rule of international relations: a State cannot ordinarily acquire treaty obligations or rights merely because other States have concluded an agreement; its consent remains essential.