In Congressional Authorization and the War on Terrorism, (1) Professors Curtis Bradley and Jack Goldsmith provide a useful framework for interpreting the contours of the 2001 Authorization for Use of Military Force (2) (AUMF). Written with the rigor and erudition characteristic of their work, the Article will no doubt make an enduring contribution to debates about the role of law in the Global War on Terrorism (GWOT). The broad, general nature of the AUMF, however, poses real challenges for any effort to define in pragmatic and principled terms the outer limits of the authority Congress has conferred on the President. Professors Bradley and Goldsmith argue that the international law of war--what we will call the law of armed conflict (LOAC)--informs the proper interpretation of the AUMF. In other words, the AUMF arguably authorizes the President to do whatever LOAC permits, in part because this well-established, widely endorsed body of law defines the rights and obligations of belligerents. We agree. (3) However, Professors Bradley and Goldsmith systematically understate the interpretive significance of LOAC and thereby blunt the sharp edges of several important law-of-war constraints on executive power.
Our aim is to offer some critical reflections on the role that international law plays in their framework. In particular, two types of problems pervade their analysis. First, they overstate the ambiguity of several relevant LOAC principles and therefore describe a legal landscape conducive to unchecked presidential power: a broad authorization to act limited only by abstract principles, the interpretation of which is the province of the President. Careful explication of LOAC principles, however, suggests several clear limits on the scope of the AUMF. (4) Second, they misspecify the range of LOAC rules that are conditions of the exercise of core war powers (such as the power to detain and the power to prosecute).
In this brief Reply, we illustrate both of these points by way of three examples. In Part I, we consider LOAC rules relevant to defining the scope of hostilities authorized by the AUMF--in particular, the class of individuals that may be treated as "enemy combatants." In Part II, we consider two controversial war powers asserted by the President: the power to detain enemy combatants and the power to try certain individuals by special military commission. In both cases, LOAC principles provide clear guidance on the scope and conditions for exercising the asserted authority. (5)
I. THE SCOPE OF GWOT: DEFINING "ENEMY COMBATANTS"
Professors Bradley and Goldsmith correctly argue that the AUMF implicitly authorizes the President to target, capture, and detain enemy combatants. The scope of the hostilities authorized by the AUMF, therefore, turns substantially on the definition of "enemy combatant." In modern LOAC, two categories of individuals may be so classified: lawful combatants (6) and unlawful combatants (civilians who directly participate in hostilities). (7) Professors Bradley and Goldsmith accurately identify the "direct participation" standard as an important aspect of this inquiry. Their analysis, however, neither adequately specifies nor usefully applies this standard. (8)
The definition of "direct participation" is much more precise--and the disagreement about its scope much less significant--than Professors Bradley and Goldsmith imply. According to the Commentaries on the Geneva Protocols, "[d]irect participation in hostilities implies a direct causal relationship between the activity engaged in and the harm done to the enemy at the time and the place where the activity takes place," (9) and it entails "a sufficient causal relationship between the act of participation and its immediate consequences." (10) Although this standard was first formalized in a treaty not ratified by the United States, there is substantial evidence that the United States has nonetheless adopted it. …