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Treaties

A treaty is defined in Article 2 of the Vienna Convention on the Law of Treaties (VCLT) 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". The definition specifies that the parties must be states, however international organisations are also considered to have the capacity to enter treaties. Treaties are binding through the principle of pacta sunt servanda, which allows states to create legal obligations on themselves through consent. The treaty must be governed by international law; however it will likely be interpreted by national courts. The VCLT, which codifies several bedrock principles of treaty interpretation, holds that a treaty "shall be interpreted in good faith in accordance with the ordinary meaning to be given to the terms of the treaty in their context and in the light of its object and purpose". This represents a compromise between three theories of interpretation: the textual approach which looks to the ordinary meaning of the text, the subjective approach which considers factors such as the drafters' intention, and the teleological approach which interprets a treaty according to its objective and purpose.

A state must express its consent to be bound by a treaty through signature, exchange of instruments, ratification, acceptance, approval or accession. Accession refers to a state choosing to become party to a treaty that it is unable to sign, such as when establishing a regional body. Where a treaty states that it will be enacted through ratification, acceptance or approval, the parties must sign to indicate acceptance of the wording but there is no requirement on a state to later ratify the treaty, although they may still be subject to certain obligations. When signing or ratifying a treaty, a state can make a unilateral statement to negate or amend certain legal provisions which can have one of three effects: the reserving state is bound by the treaty but the effects of the relevant provisions are precluded or changes, the reserving state is bound by the treaty but not the relevant provisions, or the reserving state is not bound by the treaty. An interpretive declaration is a separate process, where a state issues a unilateral statement to specify or clarify a treaty provision. This can affect the interpretation of the treaty but it is generally not legally binding. A state is also able to issue a conditional declaration stating that it will consent to a given treaty only on the condition of a particular provision or interpretation.

Article 54 of the VCLT provides that either party may terminate or withdraw from a treaty in accordance with its terms or at any time with the consent of the other party, with 'termination' applying to a bilateral treaty and 'withdrawal' applying to a multilateral treaty. Where a treaty does not have provisions allowing for termination or withdrawal, such as the Genocide Convention, it is prohibited unless the right was implied into the treaty or the parties had intended to allow for it. A treaty can also be held invalid, including where parties act ultra vires or negligently, where execution has been obtained through fraudulent, corrupt or forceful means, or where the treaty contradicts peremptory norms.