Counterterrorist efforts by states are sometimes thought to be subject to different moral principles than superficially similar practices. For example, while the search for peaceful solutions is normally taken to be a moral imperative for those involved in armed conflicts, politicians sometimes make statements like ‘we do not negotiate with terrorists’, thereby denying the applicability of the imperative in conflicts involving terrorist groups. In order to see whether this sort of view is justified, we need to be clear about what we mean when we talk about terrorism. Both normative elements (which explain how terrorism is morally distinct from other sorts of harmful actions) and descriptive elements (which explain how terrorist groups differ sociologically from other groups) may be significant in thinking about what moral limits should be maintained when combating terrorism.

Three state institutions that are often involved in counterterrorist activities are the military, the police, and the criminal justice system. The actions of all three raise significant ethical questions that have been the subject of debate. When militaries use deadly force against terrorists, we need to determine whether their actions are best understood as acts of war (and therefore subject to principles of just war theory or something similar) or policing operations (subject to different requirements). When the police pursue terrorists, the question of whether set-backs to liberty are justified by increases in security looms large. Finally, in the criminal justice system, issues concerning what rights should be granted to terrorist suspects in custody, and how terrorism should be punished, need to be considered in light of many governments’ policies in this area.