Most commentary on the President's constitutional power to utilize military force abroad omits any discussion of international law. The constitutional limitations on such Executive power are viewed as stemming from Congress's article I, § 8 war powers, not from any proscriptions based upon international law. Even some scholars who generally recognize that international law is part of our law view the President's constitutional powers as Commander in Chief and "sole organ of foreign affairs" as providing the Executive with the constitutional authority to use force in violation of international law.1
This chapter will argue that the President's foreign affairs power is constitutionally limited by international law norms. These limitations apply in two general areas. The first is the President's conduct of a war. The President's choice of weaponry within a war ought to be constitutionally circumscribed by international norms. To the extent that international law prohibits the first use of nuclear weapons or the use of biological or chemical weapons, or intentionally bombing civilians, the President's constitutional power as Commander in Chief to conduct a war is accordingly limited. Second, the President's asserted constitutional power to use limited military force against foreign nations--assassinating foreign leaders, bombing other nations to achieve certain foreign policy goals, invading another country to bring its leader back to the United States for trial, initiating covert paramilitary warfare--is also circumscribed by international law. While I have elsewhere argued that Congress's article I, § 8 war powers prevents such unilateral presidential use of force,2 an additional constitutional limitation deriving from international law also exists. In sum, international law and constitutional law are not two separate spheres; rather the interplay between the two bodies of law must inform our definition of and limitations on Executive power.
The end of the Cold War creates both a better opportunity for and a greater importance to recognizing the interplay between international norms and constitutional distributions of power. Many of the arguments opposing international law