In relation to a treaty, a third state is ‘a state not a party to the treaty’ (Article 2(1)(h)). A range of states falls within this definition, from one which is not eligible to become a party, to a state which has ratified but for which the treaty is not yet in force. Third states should not be confused with objects of international law, such as corporations and individuals. Although some treaties confer important rights on them, that does not make them third parties. Although the rules in the Convention rest firmly on the sovereignty and independence of states, similar rules apply in the law of contract, and, as with them, the third state probably has to be identifiable either by name or as a member of a certain class or as answering to a particular description. (For the situation when an international organisation – either alone or with some or all of its Member States – is party to a treaty, see pages 417–19 below.)

General rule

The general rule is rather obvious: a treaty does not create either obligations or rights for a third state without its consent (Article 34). Thus a treaty, whether bilateral or multilateral, cannot, by its own force, impose an obligation on a third state, nor modify in any way the legal rights of a third state without its consent.