PART III. OBSERVANCEs APPLICATION AND
INTERPRETATION OF TREATIES
SECTION 1. OBSERVANCE OF TREATIES
Article 26
Pacta sunt servanda faith.
Every treaty in force is binding upon the parties to it and must be performed by them in good
Article 27
Internal law of States, rules of international organizations
and observance of treaties
1. A State party to a treaty may not invoke the provisions of its internal law as justification for its failure to perform the treaty.
2. An international organization party to a treaty may not invoke the rules of the organization as justification for its failure to perform the treaty.
3. The rules contained in the preceding paragraphs are without prejudice to article 46.
SECTION 2. APPLICATION OF TREATIES
Article 28
Non-retroactivity of treaties
Unless a different intention appears from the treaty or is otherwise established, its provisions do not bind a party in relation to any act or fact which took place or any situation which ceased to exist before the date of the entry into force of the treaty with respect to that party.
Article 29
Territorial scope of treaties
Unless a different intention appears from the treaty or is otherwise established, a treaty between one or more States and one or more international organizations is binding upon each State party in respect of its entire territory.
Article 30
Application of successive treaties relating to
the same subject matter
1. The rights and obligations of States and international organizations parties to successive treaties relating to the same subject matter shall be determined in accordance with the following paragraphs.
