1. The Law of Treaties

2. What is a treaty?
A treaty is 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 (1969 Vienna Convention on the Law of Treaties, Article 2).

3. The Types of Treaties Classification by level: Inter-State treaties
Intergovernmental treaties
Inter-ministerial (inter-agency) treaties
Classification by number of parties:
Bilateral
Multilateral

4. Modes of expressing consent
Consent by signature
Consent by ratification
Consent by acceptance / approval
Consent by exchange of instruments
Consent by accession

5. Reservations to treaties
A reservation is a unilateral statement, however phrased or named, made by a State, when signing, ratifying, accepting, approving, or acceding to a treaty, whereby it purports to exclude or to modify the legal effect of certain provisions of the treaty in their application to that State (Vienna Convention 1969, Article 2).
NB: reservations vs. understandings, political statements or interpretive declarations.
NB: object and purpose of the treaty in question!!!

6. The entry into force of treaties
Entry into force – in accordance with treaty provisions
Registration in the UN Secretariat and publication

7. The application of treaties
Pacta sunt servanda
Application of successive treaties
Third States

8. The amendment and modification of treaties
Amendment – procedure applicable all parties to a treaty
Modification – procedure applicable to a number of parties to a treaty

9. The interpretation of treaties
Textual (literal) interpretation
Circumstantial interpretation (traveaux preparatoires)
Teleological (purpose-related) interpretation

10. The invalidity of treaties
Municipal law
Error
Fraud and corruption
Coercion
Jus cogens

11. The termination of treaties
Termination by treaty provision or consent
Material breach
Supervening impossibility of performance
Fundamental change of circumstances (rebus sic stantibus)