Treaty signifies the discussion of terms which immediately precedes the conclusion of a contract or other transaction. A warranty on the sale of goods, to be valid, must be made during the treaty preceding the sale. In public and international law a treaty is an agreement between the Governments of two or more states. Such an agreement is obviously not enforceable by legal proceedings. In England the power of making treaties with foreign states is vested in the Crown as part of the prerogative of the Sovereign. In some cases, however, treaties made by the Crown are not valid in the Courts of this country unless concluded under the powers of an Act of Parliament - for instance, extradition (q.v.).