 The United States Constitution, effective in 1789, gave the Federal government power over foreign affairs and restricted the individual States'authority in this realm. Article I, section ten provides, "no State shall enter into any Treaty, Alliance, or Confederation" and that "no State shall, without the Consent of the Congress. .. enter into any Agreement or Compact with another State or with a foreign Power." The Federal government's primacy was made clear in the Supremacy Clause of Article VI, which declares, "This Constitution, and the laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the authority of the United States, shall be the Supreme Law of the land; and the Judges in every state shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding." While executive agreements were not mentioned in the Constitution, Congress authorized them for delivery of the mail as early as 1792.
