A treaty is a compact between two independent governments, determining rights or privileges between them as sovereigns; or between each and the subjects of the other; or between the subjects of one and the subjects of the other. In the United States the treaty-making power is vested by the constitution in the president, who negotiates the treaty through the regular diplomatic representatives of the government, or special representatives appointed for the purpose; but it does not become a complete treaty except by the advice and consent of the Senate, concurrence of two-thirds of the senators present when the treaty is acted upon being necessary to its approval (Art. II, § 2, ¶ 2). Even then it must be promulgated by the executive department after it has also been ratified by the other contracting power.

A treaty may be self-executing, or it may involve legislative action in order that its provisions may be carried into effect. In the latter case the necessary legislation must be provided by Congress, and the House of Representatives, by refusing to concur in legislation proposed for that purpose, may defeat the execution of the treaty. While it may perhaps be said that it is in a general sense the duty of Congress to carry out the provisions of a treaty by necessary legislation, and the national honor may require that it do so, nevertheless that is a matter for the exercise of legislative discretion, and if the House of Representatives refuses to act, or imposes conditions not ineluded in the treaty itself, there is no means provided for controlling its action. Thus, if a treaty involves the payment of money, it can only be carried out by the concurrence of the House of Representatives in an act appropriating money from the public treasury for the purpose.

The treaty-making power is practically without limit, so far as it is exercised with reference to matters which may be regulated by treaty, and it extends to all proper subjects of negotiation between our government and the governments of other nations. Its limitations are to be found only in its nature and the nature of the federal government, as defined by the federal constitution. It could not be used for the purpose of changing the character of the federal government, or determining its relations with a state government. But whatever limitations there may be on the treaty-making power, they are implied, and are nowhere expressed in the federal constitution.