Public International Law

Treaties are the principal source of Public International Law.

The Vienna Convention on the Law of Treaties defines a ‘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(1)(a)).

A treaty is an agreement between sovereign States (countries) and in some cases international organisations, which is binding at international law. An agreement between an Australian State or Territory and a foreign Government will not, therefore, be a treaty. An agreement between two or more States will not be a treaty unless those countries intend the document to be binding at international law.

Treaties can be bilateral (between two States) or multilateral (between three or more States). Treaties can also include the creation of rights for individuals.

Treaties are commonly called 'agreements', 'conventions', `protocols' or `covenants' , and less commonly `exchanges of letters'. Frequently, `declarations' are adopted by the UN General Assembly. Declarations are not treaties, as they are not intended to be binding, but they may be part of a process that leads ultimately to the negotiation of a UN treaty. Declarations may also be used to assist in the interpretation of treaties.

The Law of Treaties

The 1648 Peace Treaties of Westphalia established the framework for modern treaties and recognised the right of the sovereign to govern free from outside interference.

The Vienna Convention on the Law of Treaties is the UN agreement that codifies the rules that guide treaty relations between States. The Convention provides an international legal framework for these relations in times of peace (the effect on treaties of the outbreak of hostilities between States is explicitly excluded from the reach of the Convention). This framework includes the rules on the conclusion and entry into force of treaties, their observance, application, interpretation, amendment and modification, and rules on the invalidity, termination and suspension of the operation of treaties. By providing this legal framework, the Convention promotes the purposes of the UN set forth in its Charter, including the maintenance of international peace and security, the development of friendly relations between states and the achievement of cooperation among nations.

The treaty text may provide for the manner by which it takes effect. Generally, treaties will enter into force when it has been signed and ratified by a certain number of parties. Parties to a treaty may ratify a treaty with reservations or other declarations unless the terms of the treaty place restrictions on those actions. A reservation is a country's attempt to modify certain terms of the treaty, as it applies between itself and other countries.

Multilateral treaties are published in sets such as the United Nations Treaty Series (UNTS). Only treaties deposited with the UN Secretary-General become part of the UNTS. Although most multilateral (and many bilateral) treaties are deposited with the UN as a matter of course, states are under no specific obligation to do so. A good source of information on the role of the UN as a treaty depository is the Summary of Practice of the Secretary-General as Depository of Multilateral Treaties on the UN website.

Summary of Practice of the Secretary-General as Depository of Multilateral Treaties on the UN website.