International Law and State Systems

International law is an extra system on top of the state systems. It presupposes state law, and could not exist without it, because international law can only be enforced if states are prepared to put it into effect. But it serves a different community: the international community, international law is about the relations between independent states. It treats them as equals, whatever their population, wealth and power, so that in international law Barbados is on a level with Japan-like state law. International law consists of several elements. Again all of them aim at stability in international life and the encouragement of trade and other contacts between states. International law lays down how international bodies such as the United Nations are set up, and what powers they have (their constitution). It also says how states must treat one another, how they must behave to international bodies and how the international bodies must behave towards them. It provides facilities for states to make binding agreements (treaties) and for the settlement of disputes. International law can be enforced only when the states accept the power of a court to decide whether the law has been violated.

International conventional obligations, both bilateral and multilateral, are all regulated by the same general principles of international law. For the greater part, these are contained in the Vienna Convention on the Law of Treaties 1969.

The Vienna Convention is limited in application to treaties between states, although it can be applied as customary international law to agreements between non-state entities such as international organizations (Article 3).

The Convention defines the term ''treaty'' 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'' (Article 2). The term means all international agreements, protocols, exchanges of notes, declarations, etc. regardless of designation. Although the Convention only refers to written agreements, valid obligation may also be constituted on an oral basis.

The Convention promotes the use of written agreements in order to discourage oral agreements which are more susceptible to misinterpretation. In practice, unwritten agreements are limited by Article 102 of the UN Charter which stipulates that ''every treaty... entered into by any Member of the United Nations... shall as soon as possible be registered with the Secretariat and published by it... (and)... no party to any such treaty... which has not been registered... may invoke that treaty or agreement before any organ of the United Nations.''

In order for a treaty to be valid, it must be adopted by the free consent of the contracting parties. Consent may be expressed by signature, exchange of instruments constituting a treaty, ratification, acceptance, approval or accession, or by any other means if so agreed.