The current US conflicts in Iraq and Afghanistan are characterized by enemies who regularly disregard international law and just war principles. Asymmetric conflicts such as these, in which belligerents violate laws of war to gain an advantage over a superior military force, are likely to be the norm for the foreseeable future. When such opponents refuse to "play by the rules," are there rules which the United States may then justifiably set aside? This normative paper examines jus in bello principles within just war theory to provide recommendations for US forces faced with this situation. The restrictions based on discrimination and proportionality must remain intact, but the US interpretation of military necessity must be altered from traditional views that have historically led to immoral decisions in the conduct of war. Military necessity must be considered at all levels of war, and the justice of the cause must not be used to justify gradual violations of jus in bello when selecting the tactics. Fighting with strict adherence to these just war principles is not only vital to securing domestic and international support for the US military, but it directly affects our ability to achieve current and future military objectives.