A reservation must be communicated to the contracting States or IGOs and other States or IGOs entitled to become parties to the relevant treaty in order to ensure that they can formulate an objection to it within a period of 12 months after being notified of it.
General rule of a treaty: reservations are allowed exceted in package-deal treaties. Two are the classes of revervations to treaties (see article 19 &20 VCLT):
- Permissible reservations: expressely permitted by the relevant treaty and those which are compatible with the object and purpose of that reaty. Reservations operate on the basis of reciprocity and, if they are permissible, create the following relationships between the reserving State and the other contracting States.
- Non-permissible reservations: the ones prohibited expressely or implictly by the concerning treaty, and reservations which are incompatible with the object and purpose of the relevant treaty.
Objection. Any signatory or contracting state has the option of objecting to a reservation, inter alia, if, in its opinion, the reservation is incompatible with the object and purpose of the treaty. The objecting state may further declare that its objection has the effect of precluding the entry into force of the treaty as between objecting and reserving states. [Art.20-23, Vienna Convention on the Law of Treaties 1969]