The United States, while taking the position that there is no per se rule banning the use of nuclear weapons, acknowledges that the use of such weapons is subject to the law of armed conflict, including the rules of proportionality, necessity, moderation, discrimination, civilian immunity, neutrality, and humanity.96 As has been noted, some of the effects of nuclear weapons can be similar to a worst case cyber attack on a state. In an all-out attack, all critical infrastructure could be disabled or destroyed, leaving the victim nation completely helpless and its population terrorized or worse.
Cyber attacks on the scale of Estonia, like nuclear warfare, do not discriminate between combatants and non-combatants, nor do they pass the test of proportionality. If the use of nuclear weapons is subject to the rules of IHL listed above, as the U.S. maintains, so too should cyber attacks. Even though the ICJ did not declare all nuclear weapons illegal, the logic of its holding that “methods and means of warfare…which would result in unnecessary suffering to non-combatants, are prohibited”97 is just as applicable to cyber war as it is to nuclear war. Cyber attackers are in fact conceivably even more responsible for non-combatant casualties than is a nuclear aggressor state launching a mass assault, since cyber attacks by their nature may be targeted to specific systems whereas nuclear weapons cannot be similarly focused. Even the lowest yield weapons result in substantial collateral damage.98 Yet the ICJ has refused to rule such low-yield nuclear weapons illegal. As this decision indicates, there is as of yet little to no customary international law pertaining to the use of cyber attacks beyond the basic
96 On the Unlawfulness of the Use and Threat of Nuclear Weapons, Report of the Foreign and International Law Committee of the New York County Lawyers’ Association, available at: . Last visited: Feb. 24, 2008.
97 Nuclear Weapons Advisory Opinion ¶ 95, at 32, 35 I.L.M. at 829.
98 Robert W. Nelson, FAS Public Interest Report - Low-Yield Earth-Penetrating Nuclear Weapons, Federation of American Scientists, Apr. 19, 2008. Available at: . Last visited: 4/20/2008.