Certain sages these days tell us the president has vast, almost unlimited powers in the area of foreign policy. Since the supposed genius of our system of government is its checks and balances, this proposition strikes me as exceptionally strange.
Article II, Section 2 of the Constitution assigns the president three powers related to foreign policy: commander in chief, making treaties and appointing ambassadors. A requirement that two-thirds of senators approve any treaty and that the Senate approve any ambassadors are substantial limits on those powers.
On the other hand, Article 1, Section 8 of the Constitution grants the Congress at least nine specific powers related to foreign policy, including paying for national defense, declaring war, regulating commerce with foreign nations, and enacting rules for the regulation of the armed forces.
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While "vast," "almost unlimited" presidential powers in the area of foreign policy may derive from wishful thinking, partisan propaganda or abuse of office, they almost certainly do not derive from the Constitution.
Paul Sherman, Madison