I.

Introduction

Treaty, in international law, written agreement concluded by two or more sovereign nations or by a nation and an international organization, such as the European Union. The power to enter into treaty relations is an essential attribute of sovereignty. The principle that treaties validly concluded are binding on the signatories, who must adhere to them in good faith, is a cardinal rule of international law.

II.

Validity

The usual conditions essential to the valid conclusion of a treaty are that the contracting parties must have the requisite capacity to enter into international engagements, the plenipotentiaries who negotiate the treaty must be properly authorized, and freedom of consent on the part of the signatory powers must exist. It is now recognized that a treaty is void if its conclusion has been procured by the threat or use of force in violation of the principles of international law embodied in the United Nations (UN) Charter.

Peace treaties concluded after the cessation of hostilities were usually considered not to be void because of the preceding warfare. Nevertheless, in 1932 the United States established a policy against recognizing any treaty or agreement brought about by means contrary to the Kellogg-Briand Pact. This principle, known as the Stimson Doctrine, was adopted by the League of Nations. Similar principles were included in the 1969 Vienna Convention on the Law of Treaties.

III.

Content

On the international level, the scope of the treaty-making power of a state is practically unlimited. It includes the acquisition of foreign territory, the cession of domestic territory, the delimitation and rectification of boundaries, the promise of mutual assistance, the guarantee of foreign investments, and the extradition of people accused or convicted of crimes. Treaties may be of a law-making character and of a multilateral nature, such as the conventions on the law of the sea, on human rights, and on the privileges and immunities of diplomatic missions and their staff. Multilateral treaties are also the basis for the establishment of international organizations and the determination of their individual functions and powers.

IV.

Types of Treaties

Many treaties can be classified as either political or commercial agreements. Political treaties may relate to mutual defence in case of armed attack; to guarantees of a particular status, such as neutrality; or to the preservation of existing boundaries. Treaties of alliance that promised mutual support in the event of war are no longer valid to the extent that they violate the UN Charter. Commercial treaties usually provide mutual economic advantage, such as reduced tariffs on the imported products of the parties to the agreement. In modern times, such treaties often contain a clause stipulating that each signatory will extend to every other signatory treatment equally favourable to that accorded to any other nation (the most-favoured-nation clause). The most important multilateral treaty of that type is the General Agreement on Tariffs and Trade (GATT). The national treatment clause in commercial treaties assures equal treatment to the nationals of each signatory to the agreement. Another class of treaties provides for the submission of disputes to arbitration by special tribunals or to the adjudication of disputes by institutions such as the Permanent Court of Arbitration or the International Court of Justice.

V.

Conclusion and Ratification

International law prescribes neither a fixed form for a treaty nor any fixed procedure for its conclusion. It may be concluded by an exchange of diplomatic notes incorporating an agreed-upon text signed by authorized officials or by the signing of one or more copies of the text by officials authorized to express the consent of their respective governments to be bound by the treaty. Many important treaties require ratification by each of the contracting parties. In such cases the negotiators, after reaching agreement on the final text, sign the document and then submit the proposed treaty for ratification to the constitutionally authorized authority, usually the head of the state or the head of government.

VI.

Termination

Treaties may be terminated in various ways. The treaty itself may provide for its termination at a specified time or it may allow one party to give notice of termination, effective either at the time of receipt or following the expiration of a specified period. A treaty may be terminated by one signatory's repudiation of its obligations; such a unilateral termination, however, may provoke retaliatory measures. A treaty may also be terminated by reliance on the rebus sic stantibus principle (Latin, “things remaining that way”), that is, when the state of affairs assumed by the signatory parties (when they signed the treaty, and therefore the real basis of the treaty), no longer exists, and a substantial change in conditions has taken place.

VII.

The Vienna Convention

Rules of international law governing the conclusion, validity, effects, interpretation, modification, suspension, and termination of treaties were codified in the Vienna Convention on the Law of Treaties, adopted in 1969 at a conference convened by a resolution of the UN General Assembly. Representatives from 110 nations participated, including Great Britain, the United States, France, and most other United Nations members, as well as several non-members, including Switzerland. The draft was prepared by the International Law Commission. The convention came into force in January 1980 following ratification by 35 nations.

VIII.

UK Treaties

The power to conclude treaties rests with the Crown. This power is delegated to the executive, so government ministers can sign treaties without reference to Parliament. However, the treaty does not give rise to legal obligations in domestic law unless its provisions are expressly incorporated into national law by statute. One such example is the European Convention on Human Rights, to which Britain is a signatory, and which was incorporated into UK law by the Human Rights Act 1998.

The courts will examine treaties on the basis that Parliament cannot have intended to legislate in a way which conflicts with the country's treaty obligations; and, accordingly, if there is an ambiguity in a statute, the courts will take it to mean whatever best fits with the treaty. But if a statute is clear, the courts must enforce it even if it conflicts with the treaty.