My argument has three steps. First, I discuss the purposes of the laws of war, and argue that humanitarian considerations provide only an ambiguous rationale for limiting the weapons and tactics of warfare. Second, I discuss why some weapons and tactics are outlawed while others are not, and argue that humanitarian ideals cannot, by themselves, explain the pattern. The best explanation focuses on the enforceability of laws. I identify two conditions under which belligerents would agree on a law of war, and would be willing to comply with their agreement. The symmetry condition requires that the laws of war generate military advantages for neither belligerent. The reciprocity condition requires that each belligerent have the ability to retaliate when the other belligerent violates the laws of war. Third, I discuss the extent to which these conditions apply to the war on terror. I argue that at present they do not apply at all, but they have applied in other conflicts between governments and international terrorist organizations and could apply to the conflict between the US and al Qaeda in the future. At the outset, I should make clear that my focus is on the law, and not other considerations that might influence tactics used against enemy states or terrorist organizations. My question is whether the laws of war provide nations with a reason for curtailing strategies and tactics. I do not address the question whether independent moral or pragmatic reasons exist for behaving in ways that are not controlled by international law. For example, one might think that the US has good moral or pragmatic reasons for treating captured al Qaeda members humanely even if one concludes that it is not constrained to do so by the laws of war.
Posner, Eric A.
"Terrorism and the Laws of War,"
Chicago Journal of International Law:
2, Article 6.
Available at: https://chicagounbound.uchicago.edu/cjil/vol5/iss2/6