Over the last two decades, drones and other unmanned systems have become paradigmatic weapons of counter-terrorism. Since the end of the Clinton administration, drones have been used by the United States to conduct targeted killings - defined as the premeditated use of lethal force, by states or other armed groups, against a “specific individual who is not in the physical custody of the perpetrators". Such killings have proliferated significantly since then - the Obama administration conducted ten times more drone strikes than the Bush presidency, and the number subsequently quadrupled under President Trump, who conducted drone strikes at an average of one every 1.25 days.
The benefit of using such weapons is that America does need not sacrifice any troops to eliminate individuals regarded as an "imminent threat" to its national security. Yet, as The Economist has argued, the use of unmanned systems to assassinate individuals presents a somewhat repugnant image: that of a pilot, stationed in Nevada, who drives home for supper with his family having just blown up an Afghan wedding.
Therefore, if these weapons are to become the future of warfare, one must interrogate the concomitant ethical and legal dilemmas: what constitutes a legitimate target? Is it permissible for civilians to be killed? Are cross-border assassinations within the law? And what are the just causes for conducting drone strikes?
To first understand the legality of an action in armed conflict, one must apply the Jus ad bellum rules for when force may be initiated. In the realm of international relations, the use of force is prohibited by Article 2(4) of the United Nations Charter, with only two exceptions: action taken in self-defence, as provided by Article 51 of the UN Charter, and action taken under Chapter VII of the UN Charter, which allows the Security Council to authorise the use of force to extinguish threats to "international peace and security". For the US, it is the former that justifies their practice of targeted killing, as post-9/11, they have been engaged in armed conflict with Al Qaeda, the Taliban, and the Islamic State.
Yet the notion that America is acting purely out of self-defence is problematic. Self-defence can only be triggered by an armed attack, which the International Court of Justice (ICJ) has maintained must be of "considerable scale". 9/11 qualified as one such attack, but there are temporal limitations to which a state has the right to respond to such atrocities. Therefore, surely the United States cannot be responding to 9/11 in perpetuity.
Furthermore, to act out of self-defence is a necessary but not sufficient cause for acting legally. Article 21 of the Articles on the Responsibility of States for Wrongful Acts, articulated by the International Law Commission, states that “self-defence does not preclude the wrongfulness of conduct”. Although a state may be acting out of self-defence, it must still conform to the Jus in bello requirements laid out by International Humanitarian Law (IHL) and International Human Rights Law (IHRL). In this regard, the two key principles are proportionality and necessity.
Proportionality is the principle that an armed attack must not cause incidental loss of civilian life or damage to civilian objects that “would be excessive in relation to the concrete and direct military advantage anticipated”. However, what actions may be considered “excessive”? For example, in Pakistan from 2004-2020, a minimum of 2,515 people were killed by drone strikes, of which 424 were civilians. Is this number proportionate to the military goals achieved by the US? And would more people have otherwise been killed were it not for these drone strikes? Such questions are counterfactuals that can never be confidently answered; hence, in this regard, it is extremely difficult to judge the legality of America’s drone strikes.
The second principle for the use of force, the principle of necessity, maintains that force can only be used as a last resort. It is permissible only if taken sans the availability of more peaceful alternatives. The key justification used by the American government in this regard is that terrorists, or suspected terrorists, operating in the Middle East present an "imminent threat" to national security. The US thereby justifies its actions in terms of the Caroline Doctrine of Customary International Law, which maintains that actions taken in self-defence must be “instant, overwhelming and leaving no choice of means, and no moment of deliberation”.
The Obama administration subsequently redefined the meaning of an "imminent threat", permitting action against individuals whose terrorist plots may not even “unfold in the immediate future”. University of Oxford's moral philosopher Jeff McMahan argued that this broad definition of "imminence" is fine, because, ultimately, it is an irrelevant temporal condition that distracts from the true reason why America is hunting down these individuals: namely, that they will one day commit harm against American citizens and it would be better to kill these individuals now than risk a terrorist attack in the future.
However, American authorities often make mistakes in identifying terrorists in the first place - The New York Times quoted a senior official joking that “when the CIA sees three guys doing jumping jacks, the agency thinks that it is a terrorist training camp”. As such, to reduce civilian casualties, a narrower definition of imminent threat is necessary so that US decision-makers can be more certain that their targets are legitimate terrorists. Furthermore, action which is claimed to be taken in self-defense, but, in reality, is taken in retaliation to an armed attack, is a violation of Article 2(4) of the UN charter. Hence, when Obama sanctioned drone strikes after multiple CIA officers were killed in a suicide bomb attack in Afghanistan, his actions were expressly illegal.
Questions of legality aside, US authorities may still be able to justify drone strikes on ethical grounds. For example, US authorities have often argued that drones are more discriminate than other conventional weapons, as they limit the number of civilians that are killed in military operations. Yet, as we have already observed, mistakes are often made in identifying terrorists, and civilian casualties are still high. Hence, one must ask whether civilian casualties are ever justified? And, if so, how many?
US officials often view drone strikes within a utilitarian calculus, arguing that if more American citizens are saved than civilians are killed, then evidently, they are justified. However, do civilians not have an inviolable right to life? After all, it is not their fault that a terrorist happens to live in their neighbourhood. This is especially pertinent with regards to cases where US officials have been unsure of the identity of terrorists or of the imminence of threat. For example, Article 6 of the International Covenant on Civil and Political Rights states that "no one shall be arbitrarily deprived of his life", yet a certain element of arbitrariness exists when drone strikes take place in the absence of certainty on the identity and threat level of terrorist suspects. Hence, such drone strikes are morally unjustifiable.
However, the moral permissibility of civilian casualties is contingent upon a more fundamental question: what constitutes a just cause for the use of force? According to the precepts of just war theory there are two morally permissible justifications for war: self-defence and humanitarian intervention. The issues regarding self-defence have already been discussed. However, with regards to the latter issue, political scientist Janina Dill from the University of Oxford has argued that drone strikes (and targeted killings more generally) are justified in situations when the legitimacy of the use of force is beyond doubt, such as when intervening to prevent genocide, ethnic cleansing, war crimes, and the like. In such cases the ethical dilemma is proportionality: are the morally weighted bads (civilian deaths) less than the morally weighted goods (atrocity prevention)? If so, then drone strikes are morally permissible.
However, perhaps the strongest moral objection to the use of drones is that they lower the threshold for armed conflict. By allowing government authorities to bomb their enemies without sacrificing any troops, the political fallout from armed conflict will be minimal, perhaps increasing the proclivity of governments to use force in international disputes. This is significant because, both morally and legally, the use of force can only be justified if it is used as a last resort. However, for some, the increased use of force may be a good thing: drones allow us to fight more wars for just causes. However, is it really a good thing to encourage the extrajudicial killing of individuals who may not even be guilty? One may object that a civilized society should resort to the rule of law when settling disputes, rather than rest on the use of force. Perhaps if we want to limit wars and armed conflict in the future, then we should limit the extent to which drones may carry out targeted killings.
Overall, it is clear that drone strikes and targeted killings by other unmanned systems are justifiable on only a very limited set of legal and ethical grounds. Yet, the US government is expanding its use of such weapons, whilst also keeping such operations secret from the American public. The government no longer makes public its drone operations or the civilian casualties caused by such operations. While the concept of human rights is predicated on the principle that those who commit violations must be held to account, the US government denies the public even this most basic of principles through its refusal to grant transparency with regards to its drone operations. If drones really are to be the future of warfare, the American government needs to be kept to account for, as our analysis has shown, drone strikes and targeted killings rest on uneasy legal and ethical ground.