Not only, as we have shown, is the federal power over external affairs in origin and essential character different from that over internal affairs, but participation in the exercise of the power is significantly limited. In this vast external realm, with its important, complicated, delicate and manifold problems, the President alone has the power to speak or listen as a representative of the nation. He makes treaties with the advice and consent of the Senate; but he alone negotiates. Into the field of negotiation the Senate cannot intrude; and Congress itself is powerless to invade it. As Marshall said in his great argument of March 7, 1800, in the House of Representatives, "The President is the sole organ of the nation in its external relations, and its sole representative with foreign nations." Annals, 6th Cong., col. 613. The Senate Committee on Foreign Relations at a very early day in our history (February 15, 1816), reported to the Senate, among other things, as follows:
"The President is the constitutional representative of the United States with regard to foreign nations. He manages our concerns with foreign nations and must necessarily be most competent to determine when, how, and upon what subjects negotiation may be urged with the greatest prospect of success. For his conduct he is responsible to the Constitution. The committee consider this responsibility the surest pledge for the faithful discharge of his duty. They think the interference of the Senate in the direction of foreign negotiations calculated to diminish that responsibility and thereby to impair the best security for the national safety. The nature of transactions with foreign nations, moreover, requires caution and unity of design, and their success frequently depends on secrecy and dispatch." U.S. Senate, Reports, Committee on Foreign Relations, vol. 8, p. 24.