Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

First Advisor

Francois Tanguay-Renaud


Counterinsurgency Field Manual, International humanitarian law, Civilian direct participation in hostilities, Rules of engagement, Escalation of force incidents, Self-defense in armed conflict


This dissertation examines the problem of the mistaken killing of civilians in armed conflict. This occurs when a civilian is intentionally killed by armed forces because he or she is mistakenly believed to pose a threat of harm. The requirement that armed forces distinguish between combatants and civilians who are immune from being attacked is known as the principle of distinction in the international humanitarian law. The problem posed by distinguishing irregular fighters from ordinary civilians has long been recognized in the law, and the modern laws of war were developed, in part, to respond to this problem. At present, two of the more influential approaches to resolving the problem of distinction are the International Committee of the Red Cross (ICRC) Interpretive Guidance on Civilian Direct Participation in Hostilities, which sets out the ICRCs opinion on the circumstances under which civilian participants may be targeted, and modern Rules of Engagement, which regulate the use of force by soldiers and security forces during combat operations. This dissertation argues that both methods are inadequate to resolving the problem of distinction, because they are overbroad, in that they authorize the killing of civilians who have done nothing to forfeit their immunity, and therefore violate this key requirement of the international laws of war. This dissertation proposes a definition of civilian direct participation in hostilities that is based upon ordinary rules governing self-defense. In this way, a civilian will forfeit his or her life only when there is clear and convincing evidence that he or she is engaged in an act of aggression that wrongfully poses an imminent threat of death or serious bodily harm to civilians or members of armed forces, and the use of force is necessary and proportionate to prevent that harm. Force will be necessary and proportionate only after de-escalation of force procedures have been diligently applied, and the consequences of the use of force on the surrounding population would not be indiscriminate or disproportionate, or be such as to spread terror. Merging the rules for defensive force with the laws of armed conflict possesses several advantages over the present practice of treating self-defensive killings as being separate from, and largely superseding, international law and its norms protecting civilians. First, this approach solves the problem of providing a principled definition of civilian direct participation in hostilities, which has long been the subject of controversy and contention among states and international organizations. Second, this approach provides an explanation for why pre-emptive and status-based interpretations of civilian direct participation result in unjustified killings. Hopefully, this will be a first step in quelling the growing practice of targeting persons based upon group affiliations, both real and perceived, that is gaining legitimacy. At the same time, this approach also addresses the growing problem of mistaken killings during escalation of force incidents. At present, the international laws of armed conflict do not obligate states to use minimal force when dealing with civilians and suspected civilian participants. However, if civilian direct participation were to be based upon rules for defensive force, then minimal force and escalation of force procedures would become mandatory, rather than merely recommended, as they ensure that the killing is necessary a fundamental component of justified defensive force. Furthermore, this provides an analytical framework that can be used to analyze novel or controversial cases of civilian participation, rather than allowing states to make these decisions on an ad hoc, and largely discretionary, basis.


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