Reservation (law)

A reservation in international law is a to a state's acceptance of a treaty. A reservation is defined by the 1969 Vienna Convention on the Law of Treaties (VCLT) as:

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. (Article 2 (1)(d))

In effect, a reservation allows the state to be a party to the treaty, while excluding the legal effect of that specific provision in the treaty to which it objects. States cannot take reservations after they have accepted the treaty; a reservation must be made at the time that the treaty affects the State. The Vienna Convention did not create the concept of reservations but codified existing customary law. Thus even States that have not formally acceded to the Vienna Convention act as if they had. As reservations are defined under the Vienna Convention and interpretative declarations are not, the two are sometimes difficult to discern from each other. Unlike a reservation, a declaration is not meant to affect the State's legal obligations but is attached to State's consent to a treaty to explain or interpret what the State deems unclear.

The Articles 19–23 of the Vienna Convention details the procedures relating to reservations. To see if a reservation is valid the legality of the reservation test applies as described in article 19 of the Vienna Convention. According to this article a state may not formulate a reservation if:

1: The reservation is prohibited by the treaty. (e.g. the Supplementary Convention on the Abolition of Slavery and Convention against Discrimination in Education)
2: The treaty provides that only specified reservations, which do not include the reservation in question, may be made.

3: In cases not falling under (1) or (2), the reservation is incompatible with the object and purpose of the treaty.

A reservation must be put into writing and then sent to the either the depository of the treaty, in the case of a multilateral treaty, or directly to the other States party to the treaty

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