Written agreement between two or more states. Treaties take effect either immediately on signature or, more often, on ratification. Ratification involves a further exchange of documents and usually takes place after the internal governments have approved the terms of the treaty. Treaties are binding in international law, the rules being laid down in the Vienna Convention on the Law of Treaties 1969.
The binding legal quality or a treaty is not dependent upon any particular form, and such an agreement may be described by other labels including the terms: convention, pact, covenant, charter, or act. Frequently a treaty will provide that there will be two specific stages involved in the achievement of a binding agreement, referred to as the signature and ratification. In such cases treaties may be signed after their formal negotiation, but will only become legally binding on ratification.
Ratification Contemporary treaty-making practice includes the technique of providing that the agreement will only enter into legal force when a minimum number of parties have ratified the treaty. This is intended to ensure that the legal rules laid down therein will govern the behaviour of a significant group of states. The treaty-making power in the UK rests on the Crown. Thus treaties are made by the Crown, that is the Queen acting on the advice of her ministers, with the representatives of the supreme authority of the state with whom the treaty is agreed.
In general treaties do not require parliamentary approval, although since 1924 it has been the practice to lay treaties between heads of state before Parliament for a period of 21 days prior to ratification by the Crown. This is known as the Ponsonby rule. However, some treaties are made expressly subject to parliamentary confirmation (for example, Britain's acceptance of the Treaty of Rome). Other treaties require changes in the law and these may precede or follow the making of a treaty (for example, the European Communities Act 1972 implemented Britain's signing of the Treaty of Rome and entry into the European Economic Community).
In practice, governments do not normally enter treaty obligations unless they are confident of support in Parliament and parliamentary opinion is often tested by debate and resolution prior to treaty agreements. The legal significance of a treaty commences, according to international law, from the time the parties intend it to enter into force. Whether the rules it creates will have legal significance within the law of a particular party to the treaty will depend upon that law. In the UK, British courts will only implement a treaty to the extent that Parliament has provided for such implementation. In the USA, treaties are negotiated by the president but must be ratified by the Senate. However, so-called executive agreements which in many cases result in an agreement with another state, binding under international law, may be made without such approval. As such they become part of the law of the land, though their implementation may be difficult without congressional approval.
The use of force A major feature of the international law of treaties, prior to the existence of the United Nations charter, was that though a treaty was created by agreement between parties, the fact that one had induced the other to enter the arrangement by duress would not vitiate the treaty. Obvious examples of the utility of such rule are the many peace treaties made between victor and vanquished states.
In an international legal system such as that established by the combination of the United Nations charter and the Kellogg–Briand Pact (1928), which in law prohibited war and the use of force (other than in very limited circumstances), such a rule has undergone modification. The law of treaties generally has undergone significant development and codification since the establishment of the United Nations Organization, culminating in the Vienna Convention (1969) on the law of treaties. This establishes the rule that any treaty produced as a result of the use or threat of force contrary to the United Nation charter shall be void.
Multilateral treaties Treaties are frequently compared with contracts on the one hand and legislation on the other, as they exist in municipal (or national) legal systems. In fact a treaty creates legal obligations only for the parties to it, and does not bind non-parties. Multilateral treaties such as the United Nations charter, binding the overwhelming majority of states, are sometimes referred to as law-making treaties, since they effectively lay down rules for the majority of the subjects of the international legal system, and are often widely acquiesced in by non-parties, or are accepted as correct statements of rules of international customary law.
Strictly speaking however, a particular treaty can only create law for the parties, and the generalization of its rules occurs through processes other than the law of treaty. The United Nations charter is an exceptional case among treaties, partly because of the number of parties, and partly because the states establishing the organization have purported to grant it authority to impose its will in the field of collective security upon non-members, as well as obliging members to treat their obligations to the organization as overriding all others. In this way the states, as members of contemporary world society, have taken a step towards the establishment of a world order by mutual agreement.
International law Treaties have played a significant role in the development of international law since the advent of the International Law Commission of the United Nations Organization. This body, in carrying out its function of developing and codifying the law, has evolved and put forward to diplomatic conferences important treaties to clarify law by would-be multilateral treaties in such fields as the law of the sea (Geneva Conventions 1958), the law of diplomatic relations (Vienna Convention 1961), and the law of treaties itself. Treaties as a source of rules of international law have also been given an added importance by virtue of the large number of new subjects of international law which have been created since the birth of the United Nations, many of which are socialist states.
The fact that existing international law created largely in an era of laissez-faire capitalism is to some extent unacceptable to such states, makes the agreed codification of a mutually acceptable system of rules established by treaties most important.
Jay Treaty, 1794
Treaty of Greenville, 1795