In the broad sense, a treaty is an accord concluded between members of the international community. These are generally states, although sometimes they are political entities seeking to become states (for example, Britain's American colonies in 1776). In the latter case, signing a treaty with the entity gives it the character of a state. According to this broad definition, a treaty is neither a law, which is internal as opposed to international, nor a contract, which is private (or is concluded between a state and a person or an organization). This was the case in the Lake Success Accord of 26 June 1947 between the United Nations and the United States, regarding the location of the permanent headquarters of the United Nations.
In the strict sense, a treaty is an international accord in which the parties involved abide by the constitutional or legal rules that, in a given state, establish treaty-making power. This is clearer in the United States than in Europe, where terminology tends to be ambiguous (the terms in use include "treaty," "convention," "pact," "charter," "statute," "act," "declaration," "protocol," "arrangement," "accord," and "modus vivendi").
In the United States the word "treaty" refers to a procedure defined in the Constitution. The president, the Constitution states, "shall have power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur." Accordingly, regardless of how they are described in ordinary language (the "Covenant" of the League of Nations, the "Charter" of the United Nations, or the Atlantic "Pact"), all international accords concluded according to this procedure are "treaties," and all others are "agreements." For the first half century after independence, all treaties, once ratified by Congress, were regarded as, in the words of the Constitution, the (supreme) Law of the Land, super-added to the laws of the land and creating individual rights and duties in all states and upheld by federal courts. Today not all treaties are so highly regarded.
The distinction between treaties and agreements is clearer in the United States than elsewhere. In the latter category it is necessary to distinguish several types. An executive agreement is an accord not approved by Congress, either before or after its signing. An example is the Korean War armistice. A congressional executive agreement is an international accord concluded by the president in accordance with a law (and, as a law, enacted by a simple majority vote of the Congress), or approved after the fact by a simple majority. Examples are the Reciprocal Trade Agreements Acts of 1934 and 1962, along with the lend-lease agreements and the European Recovery Program agreements. A joint congressional-executive action is an accord passed by joint resolution of Congress requiring only a simple majority of both houses of Congress. Examples are the annexation of Texas in 1845 and American guarantees concerning Taiwan in 1955.
The president can avoid the constitutional requirement of submitting an international accord to the Senate for approval through the use of an executive agreement. While such an agreement may concern important matters, it can take as simple a form as an exchange of letters. Sometimes it derives from the president's powers as commander in chief of the armed forces. Or it may result from a law voted by Congress giving the president the power to conclude certain accords (for example, those pertaining to the Lend-Lease Act and to the European Recovery Program, as well as postal accords and certain tariff agreements since 1934). The scope of an agreement also can extend to the recognition of states and of governments, and to the provisional or preliminary accords drawn up prior to the signing of definitive treaties.
Executive agreements were unknown in the days of George Washington, only being recognized as constitutional by the Supreme Court in 1936 and 1937. It was not until January 1972 with the Case Act (Public Law 92-403, 1 USC 112b) that Congress accepted executive agreements as constitutional, a journey begun by Senators William Knowland of California and Homer Ferguson of Michigan in 1954. The distinction between treaties and executive agreements has only domestic significance, as both are regarded as binding in international law. But there has been a vast increase in executive agreements since World War II, in part at least because of the difficulty of obtaining two-thirds Senate approval.
The increase in executive agreements also reflects the increased volume of American business with other countries, a constant and accelerated growth of governmental responsibilities imposed on all nations by technological progress, an enormous increase in the amount of power exerted throughout the world by the United States, and congressional legislation authorizing the executive branch to conclude agreements in such areas as agriculture, trade, and foreign aid. The combined necessities of skill and speed in increasingly diversified international politics have made the president of the United States, more so than was formerly true, the most important person in the world. The following statistics speak for themselves. Between 1789 and 1840, there were 60 treaties and 27 executive agreements (a ratio of 2 to 1). Between 1789 and 1940, there were 841 treaties and 1,200 executive agreements (a ratio of 2 to 3). Between 1940 and 1955, there were 139 treaties and 1,950 executive agreements (a ratio of 1 to 14). Between 1960 and 1963, there were 30 treaties and 1,132 executive agreements (a ratio of 1 to 37). A 1984 Senate study revealed that approximately 88 percent of international agreements reached between 1946 and 1972 were based on statuary authority, 6 percent were treaties, and 6 percent solely executive agreements. By the end of the twentieth century the United States was a party to more than 5,000 executive agreements and more than 950 treaties.
Treaties include all types of international agreements among sovereign states. Those agreements may be referred to as "conventions" (usually multilateral agreements), "protocols" (which expand an agreement), "charters," or even "letters." Treaties may be bilateral or multilateral, binding or nonbinding, self-executing or requiring implementing legislation. A treaty enters into force when it is deposited with an international organization or exchanges ratification with another country.
Treaties have existed for centuries, but an internationally acceptable law of treaties was not codified until the Vienna Convention on the Law of Treaties of 1969, which came into force in 1980. The United States, although not a party to the convention (it has been signed but not ratified), accepts it as setting out international law on the subject. Historically, treaties were used as instruments by states to transfer territory, settle disputes and execute other foreign policy matters (for example, to make peace). In recent history treaties have been concluded to regulate economic activities such as trade, commercial relations and intellectual property, and, increasingly, to protect international human rights, regulate pollution and protect the environment, and facilitate transnational litigation.
In the United States, the Founders gave the Senate a share of the treaty power to check presidential power. They also saw Senate involvement as a means of safeguarding the sovereignty of the states by giving each state an equal vote in the treaty-making process. The relationship between the executive branch and the Senate in the making of treaties has remained a controversial issue in U.S. foreign relations. While many presidents have sought the advice of the Senate before entering treaties or conventions, some have not. During the nineteenth century the Senate considerably extended its influence over the treaty-making process by exercising its power to amend treaties—a process begun with an amendment to Jay's Treaty in 1803—and, by the mid to late nineteenth century, requiring a simple majority vote.
Senate amendment may include reservations, understandings, interpretations, declarations, and other statements as conditions for the Senate recommendation of approval. Forty-three treaties never entered force because Senate reservations made them unacceptable to the executive or the other party(s) to the treaty, and eighty-five were withdrawn because of Senate failure to take final action on them. President William McKinley, hoping to avoid Senate rejection, which had become increasingly frequent, named three senators to negotiate the peace treaty with Spain in 1898, thereby facilitating Senate approval. Woodrow Wilson's failure to include any senators in negotiations over the Treaty of Versailles ending World War I and establishing the League of Nations was widely believed to have contributed to the Senate defeat of that treaty. Warren G Harding included senators in negotiations leading to the 1922 Washington Arms Limitation Treaty. Senators assisted in drawing up the United Nations Charter following World War II, and there were only two Senate votes against ratification.
The Senate has rejected relatively few of the treaties it has considered. It sought, with not much success, to have its deliberations kept secret. The Senate approved more than 1,500 treaties—around 90 percent of those submitted to it—in its first two hundred years. The first treaty rejected was with the Wabash and Illinois Indians in 1794, and in 1825 the Senate rejected by a vote of 40 to 0 a convention with Colombia for the suppression of the slave trade.
The flexibility of the system derives from the wide range of options it provides. In a few major instances the treaty method is required constitutionally. In the vast majority, however, the president has the principal prerogative of deciding which method will be used or attempted. Over the vast network of events, times, ideas, attitudes, and strength relationships of the political parties, a decision on the preferred method in all given types of instances rests upon calculations virtually approaching infinity.