Law of Treaties — Vienna Convention 1969
The Vienna Convention on the Law of Treaties 1969 (VCLT) is the principal codification of the law governing treaties between states. Adopted on 22 May 1969 and in force from 27 January 1980, it has 85 articles arranged in eight parts. Even non-parties (e.g. the USA) treat much of the VCLT as customary international law, as confirmed in the Namibia Advisory Opinion ICJ 1971.
Article 2(1)(a) 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'.
Conclusion and entry into force
Treaty-making proceeds through stages:
- Negotiation — by accredited representatives bearing full powers (Art. 7).
- Adoption of text — by consent of all participants, or by two-thirds majority at international conferences (Art. 9).
- Authentication — by initialling or signature ad referendum (Art. 10).
- Consent to be bound — by signature, ratification, acceptance, approval or accession (Arts. 11–16).
- Entry into force — as the treaty provides or as the parties agree (Art. 24).
- Registration with the UN Secretariat (UN Charter Art. 102; VCLT Art. 80) — failure does not invalidate but prevents invocation before UN organs.
Until ratification, signatory states must refrain from acts that would defeat the object and purpose of the treaty (Art. 18 — Interim Obligation).
Reservations (Arts. 19–23)
A reservation is a unilateral statement made by a state when signing, ratifying or acceding, purporting to exclude or modify the legal effect of certain provisions in their application to that state (Art. 2(1)(d)). A reservation is permitted unless:
- The treaty prohibits it.
- It falls outside the categories the treaty allows.
- It is incompatible with the object and purpose of the treaty.
The Reservations to the Genocide Convention Advisory Opinion ICJ 1951 introduced the object-and-purpose test, displacing the earlier unanimity rule.
- Acceptance of a reservation (Art. 20): expressly, tacitly (12 months), or by another party's non-objection.
- Objection without precluding entry into force: provisions to which reservation relates do not apply between objecting and reserving state (Art. 21(3)).
- Withdrawal of reservations or objections — possible at any time (Art. 22).
- Human-rights treaty reservations — special regime under General Comment 24 of HRC (1994) and ILC Guide 2011.
Observance and application (Arts. 26–30)
- Article 26: pacta sunt servanda — treaties in force are binding and must be performed in good faith.
- Article 27: a state may not invoke its internal law as justification for failure to perform.
- Article 28: non-retroactivity unless otherwise indicated.
- Article 29: territorial scope — entire territory unless otherwise provided.
- Article 30: successive treaties on the same subject matter.
Interpretation (Arts. 31–33)
Article 31 lays down the general rule: a treaty shall be interpreted in good faith, in accordance with the ordinary meaning of its terms in their context and in the light of its object and purpose.
Article 32 permits supplementary means — preparatory work (travaux préparatoires) and circumstances of conclusion — to confirm or determine the meaning when Article 31 leaves it ambiguous or absurd.
Article 33 governs treaties in two or more languages — each text equally authentic unless otherwise provided.
The WTO Appellate Body in US – Shrimp (1998) and the ICJ in LaGrand Case (2001) confirmed Article 31 as customary law.
Amendment and modification (Arts. 39–41)
- Amendment between all parties — by agreement (Art. 39); multilateral treaties under Art. 40.
- Modification between some parties (Art. 41) — permitted if (i) provided for in the treaty or (ii) compatible with object and purpose and not affecting other parties' rights.
Invalidity, termination and suspension (Arts. 42–72)
The grounds form a closed list:
| Ground | Article | Effect |
|---|---|---|
| Provisions of internal law on competence | 46 | Voidable only if manifest |
| Specific restriction on representative's powers | 47 | Voidable |
| Error | 48 | Voidable; bar if state contributed |
| Fraud | 49 | Voidable |
| Corruption of representative | 50 | Voidable |
| Coercion of representative | 51 | Void |
| Coercion of state by force | 52 | Void |
| Jus cogens conflict | 53 / 64 | Void / void at the time of new norm |
| Material breach | 60 | Termination/suspension |
| Supervening impossibility | 61 | Termination |
| Fundamental change of circumstances (rebus sic stantibus) | 62 | Termination — strict |
| Severance of diplomatic relations | 63 | Generally does not affect treaty |
The Gabčíkovo-Nagymaros Case ICJ 1997 narrowly construed Article 62 (rebus sic stantibus).
For CSS, a treaties question almost always includes one of these threads: (i) reservations (cite Genocide Convention 1951); (ii) interpretation (cite Article 31 + LaGrand 2001); (iii) termination on material breach or rebus (cite Gabčíkovo-Nagymaros 1997); (iv) jus cogens (cite Articles 53 and 64). Always start with Article 2(1)(a) for definition.
Treaties and third states (Arts. 34–38)
Pacta tertiis nec nocent nec prosunt — a treaty does not create obligations or rights for a third state without its consent. Exceptions:
- Obligation for third state (Art. 35) — express acceptance in writing.
- Right for third state (Art. 36) — assent presumed unless contrary.
- Codification of customary rules binding on all (Art. 38).
Reservations and Pakistan's practice
Pakistan made reservations to the ICCPR and CAT at ratification (2010), which were challenged as incompatible with object and purpose by several states. Pakistan withdrew several reservations to the ICCPR in 2011, retaining those to Articles 3, 6, 7, 12, 13, 18, 19, and 25 in modified form. The Pakistani Supreme Court in Société Generale de Surveillance v. Pakistan PLD 2002 SC 491 addressed the relationship between treaties and municipal law, requiring legislative implementation.