The answer is the advice and consent of the Senate. The President’s power to create treaties is restricted by the measures required by the Treaty Clause. This clause gives the President the “Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present agree.” This places a clear limitation on the President’s power to make treaties: if less than two-thirds of the Senators present agree that the treaty should be made, then the United States has not go through any treaty. The President therefore cannot individually enter into a treaty.
