The recent film Eye in the Sky brings to mind concerns over the use of remotely piloted vehicles, more popularly known as drones, in the war on terror: the kill lists bearing the names of American citizens and drawn up by unknown committees in the CIA; the buzz of the aircraft hovering over Pakistani villagers, waiting to see whom will receive death from above; the anonymous men and women who inflict that death from far away, as if they were playing a computer game. And yet drones have become such a popular weapon in the American arsenal precisely because they are capable of efficient, targeted killing without endangering American soldiers. How can drones be best employed to keep Americans, as well as civilians of other countries, safe?

Kenneth Himes’ Drones and the Ethics of Targeted Killing takes up this question and offers an ethical and theological analysis of how we do and should use drones: ethical because Himes is concerned not simply with whether our use of drones is legal, but whether or not it obeys laws deeper than those of our own making; theological because Himes grounds his investigation in the historical sources of the Christian just war tradition.

Himes’ primary argument is that drone attacks are a species of targeted killing, and that clarity about that type of action helps us better assess the rights and wrongs of counter-terrorism. Himes defines targeted killing as a lethal action by agents of a state or party in an armed conflict that “is not accidental or random and [in which] the victim is not under the control of the killer.” Moreover, “The use of targeted killing also claims to satisfy an authorized legal standard.” In this sense, targeted killing is different from assassination, which is done in peace time and for a political motive, and from execution, which is done to a captive by those holding him in custody.

Having defined his terms, Himes looks at the history of ethical reflection in Greco-Roman, Jewish, and Christian thought. Greek and Roman authors focused on tyrannicide, the assassination of an unjust ruler, which could be licit depending on who did the killing, their motive, and the nature of the tyrant. With almost no exceptions, New Testament and patristic authors saw even unjust rulers as governing in God’s stead, and God alone would judge them. Only after the killing of Thomas Becket did tyrannicide emerge as a question in Christian moral theology, and Himes offers accounts of the important figures of the debate from John of Salisbury to Alphonsus Liguori. In effect, he invites the reader into a seminar discussion he has set up. This is a great help, as his summaries are fair and succinct. However, the theological section is the least developed, and includes little from contemporary figures. More content and more direct connection of contemporary questions to theology would have helped make the book more theological.

Himes calls the theological tradition “the distant context” of the debate over drones. For the proximate context, he focuses on the Israeli Defense Force’s use of targeted killing in response to the second Intifada (2000–2005). Some commentators argued that Israel should have responded according to the norms of law enforcement, but the majority (including Himes) saw terrorist activity as a form of armed conflict to which the rules of just war would apply. Commentators outlined additional norms that should govern targeted killing, as well. For example, killing should seek to undermine the ability to launch future attacks, a category of self-defense, not simply to punish or avenge. In addition, individual responsibility must be assigned for terrorist action; being a member of an organization alone should not make one eligible for the kill list.

For the immediate context of the debate, Himes looks at the American response to terrorism. Before 9/11, Americans strongly opposed targeted killing; now America is its foremost practitioner in the world. The current policy began under George W. Bush, but expanded under Barack Obama: By the time Obama collected his Nobel Peace Prize, less than a year into his presidency, he had already personally authorized more drone strikes than Bush had in his entire presidency. Himes offers a helpful analysis of the debate that went into the killing of Anwar al-Awlaki, an American citizen who was also an al-Qaida operative, as well as the process by which targets are determined more generally, insofar as it is public knowledge.

Himes then turns to the future context, what American drone policy should be. He acknowledges that drones have been astonishingly effective at killing terrorists—particularly high-value targets whose deaths can cripple the organizations to which they belong—while minimizing civilian casualties. According to the Red Cross, 90% of casualties in most modern wars were civilian; in Pakistan (2004–2014) 11–15% were, in Yemen (2002–2014), 5–18%.

Near certainty of no civilian casualties is only one of the criteria for the Obama administration’s targeting policy. A target must also be a member of al-Qaida or an associated organization and constitute an imminent threat. However, Himes argues, the targets of drone warfare should be demonstrably high-value. The practice of signature strikes, in which people are targeted for exhibiting signature behavior instead of being thoroughly vetted and identified, must be discontinued. Indeed, for Himes, they are not true examples of targeted killing because they are not targeted at known individuals.

Furthermore, Himes argues, we should not let imminence become a slippery slope. Just because a person belongs to al-Qaida does not make him an imminent threat. Likewise, he continues, we should not allow drones simply to become a way of waging wars that cost us little in blood and treasure. According to the Justice Department, drone strikes are not violations of another state’s sovereignty if that state consents or if it is “unwilling or unable” to stop the threat posed by the target. If this is the case, Himes and others ask, how is the US not the sole arbiter of whether it can use force inside the borders of another state? Himes also argues that the US should also move all drone strikes into the military’s chain of command for the sake of transparency, instead of having some run more covertly by the CIA. We should also keep in mind that how we use drones sets a precedent for other countries—especially stronger nations such as Russia and China—and can help terrorist recruiting efforts. In short, Himes says, we should continue to employ drones in our response to terrorism, but we should proceed with justice and prudence. Readers unfamiliar with the particulars of the drone debate will benefit from his careful introduction.

Nathaniel Peters is a doctoral candidate in theology at Boston College.

Photo Credit: By U.S. Air Force Staff Sgt. N.B. Reaper being prepared for flight during Combat Hammer on May 15, 2014, at Creech Air Force Base, NV.