McNair defines treaty as “a written agreement by which two or more states or international organizations create or intend to create a relation between themselves, operating within the sphere of international law” (McNair,1961). According to Oppenheim, international treaties are agreements, of a contractual character, between states or organizations of states, creating legal rights and obligations between the parties (Oppenheim, vol. I, 1992). The Vienna Convention defines treaty as “an international agreement concluded between states in written form and governed by international law” (Art. 2(1)/a).