Observance of treaty and Treaty Interpretation


• Pacta sunt servanda (Art. 26)

• No invocation of internal law as justification (Art. 27)

• No retroactivity of treaties (art. 28)

• Territorial scope of treaties (art. 29)

– binding to each party in respect of its entire territory



• Application of successive treaties relating to the same subject matter.

Interpretation of Treaties
• Art. 31 : general rule – Good faith / ordinary meaning / context / light of its object and purpose

– Context – to be determined by text, preamble and annexes

• Any agreement relating to treaty which was made between all parties

• Subsequent agreement regarding interpretation and application

• Relevant rules of international law applicable
• Supplementary means of interpretation (art. 32) – If the general rule makes it ambiguous or obscure or leads to the result which is manifestly absurd or unreasonable – Should interpreted in line with

• Preparatory work (Travaux Preparatories — legislative history)

• Circumstances of its conclusion