Treaties
A treaty is an agreement by States to be bound by particular rules. Interna- tional treaties have different designations such as covenants, charters, protocols, conventions, accords and agreements. A treaty is legally binding on those States which have consented to be bound by the provisions of the treaty – in other words are party to the treaty.
A State can become a party to a treaty by ratification, accession or succession. Ratifi- cation is a State’s formal expression of consent to be bound by a treaty. Only a State that has previously signed the treaty (during the period when the treaty was open for signature) can ratify it. Ratification consists of two procedural acts: on the domestic level, it requires approval by the appropriate constitu- tional organ (usually the head of State or parliament). On the international level, pursuant to the relevant provision of the treaty in question, the instru- ment of ratification shall be formally transmitted to the depositary which may be a State or an international organization such as the United Nations.
Accession entails the consent to be bound by a State that has not previously signed the instrument. States ratify treaties both before and after the treaty has entered into force. The same applies to accession.
A State may also become party to a treaty by succession, which takes place by virtue of  a specific treaty provision or by declaration.
Most treaties are not self-executing. In some States treaties are superior to domestic law, whereas in other States treaties are given Constitutional status, and in yet others only certain provisions of a treaty are incorporated into domestic law.
A State may, in ratifying a treaty, enter reservations to that treaty, indicating that, while it consents to be bound by most of the provisions, it does not agree to be bound by certain specific provisions. However, a reservation may not defeat the object and purpose of the treaty. Further, even if a State is not a party to a treaty or if it has entered reservations thereto, that State may still be bound by those treaty provisions which have become part of customary international law or constitute peremptory rules of international law, such as the prohibition against torture.