This Article answers two of the most urgent and important questions facing the contemporary law of armed conflict. First, how certain must a soldier be that a given individual is a combatant and not a civilian before attacking that individual? Second, what risks must soldiers accept to themselves and to their mission in order to reduce the risk of mistakenly killing civilians?

In the absence of clear legal rules, leading states, scholars, and practitioners have embraced a “Balancing Approach” according to which both the required level of certainty and the required level of risk vary with the balance of military and humanitarian considerations. However, this Article shows that the Balancing Approach ignores the moral asymmetries between killing and letting die and between intentionally and unintentionally killing civilians. As a result, in a wide variety of situations, the Balancing Approach would permit soldiers to intentionally kill individuals who are either probably, much more likely, or almost certainly civilians rather than combatants. These implausible implications expose the fatal defects of the Balancing Approach and demonstrate the need for a morally defensible alternative.

To meet this need, this Article develops a deontological account of both the required level of certainty and the required level of risk. The first part of this new account, “Deontological Targeting,” prohibits a soldier from intentionally killing an individual if the soldier believes the individual is a civilian, or if the soldier does not reasonably believe the individual is a combatant. These constraints establish a minimum threshold of certainty that soldiers must reach before using deadly force. Above the reasonable belief threshold, the required level of certainty varies with the relative costs of error but, crucially, also reflects the moral asymmetry between killing and letting die. In particular, except in rare cases, targeted killing operations against individuals who pose no immediate threat are permissible only if there is conclusive reason to believe that the individuals are combatants.

The second part of this new account, “Deontological Precaution,” requires, at a minimum, that soldiers take as much risk as necessary to reach the required level of certainty. In addition, soldiers must take further precautions unless doing so would increase the risk to the soldiers substantially more than doing so would decrease the risk to civilians. If soldiers are unwilling or unable to reach the required level of certainty or accept the required level of risk then they must hold their fire. The Article concludes by distilling these complex moral principles into new legal rules, reinterpretations of existing legal rules, and model rules of engagement in which soldiers can be trained and that can guide soldiers through the fog of war.

On September 16, 2007, allegedly without any provocation or justification, personnel from the security firm formerly known as Blackwater Worldwide1 fired into Baghdad’s crowded Nisoor Square and killed seventeen Iraqi civilians. To date, neither the firm nor its employees have been held accountable for this incident. Moreover, a report issued by a U.S. House of Representatives oversight panel in October 2007 indicated that “Blackwater employees had been involved in at least 196 firefights in Iraq since 2005, an average of 1.4 shootings per week.” The report also stated that in 84 percent of these incidents, Blackwater personnel were the first to fire even though, by contract, they were allowed to fire only in self-defense.

Unfortunately, Blackwater is neither the first nor the only security firm to commit human rights abuses. In the late 1990s, personnel from another security firm, DynCorp International, allegedly bought women and girls as sex slaves while deployed in Bosnia. The only punishment rendered on the personnel responsible for these human rights abuses was the termination of their employment contracts. Moreover, despite these allegations, the firm later received a contract in Iraq worth $250 million.

Laura Dickinson’s recent article in this journal substantially improves appreciation of how the United States has detained suspects and instituted military commissions as well as of the roles played by the controversial procedure and tribunals when fighting terrorism. She meticulously traces how detentions and the commissions evolved, trenchantly criticizes them, and persuasively shows international tribunals’ comparative advantage. Dickinson accords relevant domestic case precedent a somewhat laconic analysis, however. For example, she briefly mentions separation-of-powers concerns and Supreme Court opinions that detentions and military commissions implicate while rather tersely assessing Ex parte Quirin, the Second World War decision on which President George W. Bush’s Administration has heavily relied to detain suspects, to create the tribunals, and to support numerous antiterrorism initiatives, especially litigation. Dickinson suggests that closer evaluation of these critical rulings is unwarranted because they lack application for her work and others have explored the opinions. Dickinson’s treatment allows many observers, most prominently cabinet members and federal judges, to overstate Quirin and to ignore Youngstown Sheet & Tube Co. v. Sawyer.

Dickinson contributes substantially to the ongoing debate over the use of detentions and military commissions in national emergencies. She illuminates myriad complex phenomena and convincingly demonstrates how international tribunals are preferable. Her recommendation may prove superior in terms of theory, policy, and international law. Nonetheless, the very realpolitik that Dickinson so incisively criticizes, and is so clearly exemplified by the Bush Administration’s war on terrorism, mandates elaboration of the governing United States case law.