Some have called such operations ‘assassinations’. They are not, and the use of that loaded term is misplaced. Assassinations are unlawful killings.
US Attorney General, Eric Holder, 5 March 2012Footnote 1Over the last ten years, the use of drones – unmanned aerial vehicles (UAVs) or unmanned aircraftFootnote 2 – for military and counterterrorism purposes has seen ‘explosive growth’.Footnote 3 For example, it is reported that in 2010, United States President Barack Obama's administration authorized more than twice as many drone strikes in north-west Pakistan than it did in 2009 – ‘itself a year in which there were more drone strikes than during George W. Bush's entire time in office’.Footnote 4 By early 2012, the Pentagon was said to have 7,500 drones under its control, representing about one-third of all US military aircraft.Footnote 5 Use of UAVs by police forces in connection with traditional law enforcement within a state's borders has also been steadily growing, albeit at a lesser pace.Footnote 6
DronesFootnote 7 were first deployed on a significant scale for surveillance and reconnaissance in armed conflict by the United States of America: in Vietnam in the 1960s,Footnote 8 in Bosnia and Herzegovina, and Kosovo in the 1990s.Footnote 9 Most recently, in 2012, it has been reported that drones have been used by the Syrian regime to identify the location of rebel forces.Footnote 10 But although they are used in this role (and some armed forces use them only for this), they are better known for firing explosive weapons in targeted killingsFootnote 11 of suspected ‘terrorists’, especially in cross-border operations.
At the same time as scientific developments are leading to larger and faster drones, miniaturization has been paving the way for UAVs the size of insects – ‘nano’ dronesFootnote 12 – that could also be used for targeted killings, possibly using poison. In February 2011, researchers unveiled a prototype hummingbird drone, which can fly at 11 miles per hour and perch on a windowsill.Footnote 13
Robotic warfare is also on the horizon, with its obvious difficulties for establishing individual criminal responsibility (which are discussed below). In this regard, a media report in 2011 warned that fully autonomous drones, able to determine a target and fire on it without a ‘man in the loop’ (that is, independent of human control after launch), were being prepared for deployment by the USA,Footnote 14 potentially representing the greatest challenge to jus in bello since the development of chemical warfare.Footnote 15 In an internal study of drones published by the UK Ministry of Defence in 2011, it was asserted that: ‘In particular, if we wish to allow systems to make independent decisions without human intervention, some considerable work will be required to show how such systems will operate legally’.Footnote 16 Similarly, the US Department of Defense affirmed in 2009 that:
Because the Department of Defence complies with the Law of Armed Conflict, there are many issues requiring resolution associated with employment of weapons by an unmanned system. … For a significant period into the future, the decision to pull the trigger or launch a missile from an unmanned system will not be fully automated, but it will remain under the full control of a human operator. Many aspects of the firing sequence will be fully automated but the decision to fire will not likely be fully automated until legal, rules of engagement, and safety concerns have all been thoroughly examined and resolved.Footnote 17
Given that drones are clearly ‘here to stay’Footnote 18 – indeed, ‘killer drones’ are said by a former CIA lawyer to be ‘the future of warfare’Footnote 19 – this article looks at the legality of UAV strikes within and across borders,Footnote 20 and within both armed conflict and situations of law enforcement. It will thus address the interplay between jus ad bellum, jus in bello, and the rules governing law enforcement, especially international human rights law. It ends with a brief discussion of the future challenges to international law from the use of armed drones and robots.
Before embarking on more detailed discussion, however, it is worth recalling Article 36 of the 1977 Additional Protocol I, which requires that:
In the study, development, acquisition or adoption of a new weapon, means or method of warfare, a High Contracting Party is under an obligation to determine whether its employment would, in some or all circumstances, be prohibited by this Protocol or by any other rule of international law applicable to the High Contracting Party.
As a new method of warfare, the delivery of missiles by pilotless aircraft controlled by operators – often civilians – stationed thousands of miles away should already have been subjected to rigorous scrutiny by those states seeking to develop or procure drones. At the very least, the obligation set out in Article 36 should encompass all states that are party to the 1977 Additional Protocol I, although, arguably, the general obligation to ‘respect and to ensure respect’ for international humanitarian law (IHL) should incite every state, whether or not it is party to the Protocol, to conduct such legal analysis.Footnote 21 However, the seventy or more states that reportedly possess drones have not made public their own analysis – if they have conducted one – of the legality of armed drones, whether for use in armed conflict or for law enforcement purposes.Footnote 22
Drones and jus ad bellum
Jus ad bellum governs the legality of recourse to military force, including through drone strikes, by one state against another and against armed non-state actors in another state without that latter state's consent.Footnote 23 Under Article 2, paragraph 4 of the UN Charter,
[a]ll Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.
Cryer et al. describe this as the ‘fundamental legal principle governing the use of force’, which ‘reflects customary international law’.Footnote 24 However, as is also well known, under Article 51 of the Charter it is stipulated that:
Nothing in the present Charter shall impair the inherent right of collective or individual self-defence if an armed attack occurs against a member of the United Nations, until the Security Council has taken the measures necessary to maintain international peace and security.Footnote 25
The definition of an armed attack in the case of armed groups armed and equipped by a foreign state was elaborated on by the International Court of Justice (ICJ) in the Nicaragua case as follows:
The Court sees no reason to deny that, in customary law, the prohibition of armed attacks may apply to the sending by a State of armed bands to the territory of another State, if such an operation, because of its scale and effects, would have been classified as an armed attack rather than as a mere frontier incident had it been carried out by regular armed forces. But the Court does not believe that the concept of ‘armed attack’ includes not only acts by armed bands where such acts occur on a significant scale but also assistance to rebels in the form of the provision of weapons or logistical or other support. Such assistance may be regarded as a threat or use of force, or amount to intervention in the internal or external affairs of other States.Footnote 26
The threshold for the occurrence of an armed attack by another state thus appears to be relatively high, going beyond ‘a mere frontier incident’ between members of the armed forces of two states (or armed groups operating in one state with limited support from another state). It might even be argued by some that a very limited and targeted drone strike by one state against individuals located in another state would not constitute an armed attack in the sense of the UN Charter or customary law, with the argument being based on the highly contested concept of anticipatory self-defence.Footnote 27 Nevertheless, in the absence of lawful self-defence such use of armed force would undoubtedly contravene the general prohibition on the use or threat of force (and therefore amount to a violation of international law unless the use of force was consented to by the ‘victim’ state).Footnote 28 Almost certainly, a more intensive cross-border use of drone strikes, akin to a bombardment, would be an armed attack on another state and therefore constitute aggression, absent Security Council authorization or being an action being taken in legitimate self-defence.Footnote 29
However, there is a strong argument that even one drone strike constitutes an armed attack and potentially aggression. Indeed, UN General Assembly Resolution 3314 (XXIX) provided that an act of aggression shall be constituted, inter alia, by: ‘Bombardment by the armed forces of a State against the territory of another State or the use of any weapons by a State against the territory of another State’.Footnote 30 The 1988 case of nine Israeli commandos killing a single Palestine Liberation Organization military strategist in his home in Tunis, which the UN Security Council condemned as an ‘aggression’ in flagrant violation of the UN Charter, further supports the argument.Footnote 31
If a single drone strike does constitute an ‘armed attack’, the state launching the drone will need to justify its action by reference to its inherent right of self-defence (unless it had received the requisite consent or an authorization from the UN Security Council); otherwise it would be at risk of committing an act of aggression.Footnote 32 The situation is controversial when self-defence is claimed not against another state but against an armed non-state actor located in another state. In its 2004 Advisory Opinion in the Wall case, the ICJ appeared to imply that self-defence could only be invoked by one state against another state.Footnote 33 A closer reading of the dicta, though, suggests that the ICJ did not entirely rule out the possibility of self-defence against an armed non-state actor that commits ‘terrorist’ acts where effective control was not exercised by the state under threat.Footnote 34 In the subsequent Case Concerning Armed Activities on the Territory of the Congo, the ICJ avoided the question as to whether international law allows for self-defence ‘against large-scale attacks by irregular forces’.Footnote 35 A separate, minority opinion by Judge Kooijmans in this case goes further than the Wall dicta, asserting that:
if the attacks by the irregulars would, because of their scale and effects, have had to be classified as an armed attack had they been carried out by regular armed forces, there is nothing in the language of Article 51 of the Charter that prevents the victim State from exercising its inherent right of self-defence.Footnote 36
The traditional customary law governing self-defence by a state derives from an early diplomatic incident between the USA and the UK over the killing of a number of US citizens engaged in transporting men and materials from American territory to support rebels in what was then the British colony of Canada.Footnote 37 Under the so-called Caroline test, for a lawful right to self-defence there must exist ‘a necessity of self-defence, instant, overwhelming, leaving no choice of means, and no moment of deliberation’ and, furthermore, any action taken must be proportional, ‘since the act justified by the necessity of self-defence must be limited by that necessity, and kept clearly within it’.Footnote 38 These statements in 1842 by the US Secretary of State to the British authorities are widely accepted as an accurate description of a state's customary right of self-defence.Footnote 39
Therefore, the two principles of necessity and proportionality must both be met if the use of force by a state claiming to be acting in self-defence is to be adjudged lawful. Failure to meet the twin criteria means that the use of force may even constitute aggression. In its 1996 Advisory Opinion on the Legality of the Threat or Use of Nuclear Weapons, the ICJ stated that the two interdependent requirements constitute a rule of customary international law.Footnote 40 According to the principle of necessity, ‘the State attacked (or threatened with imminent attack if one admits preventive self-defence) must not, in the particular circumstances, have had any means of halting the attack other than recourse to armed force’.Footnote 41 The principle of proportionality, on the other hand, is rather more abstruse, for despite the word generally connoting a balancing (often of contrary concepts), its intent in this context is rather different:
The requirement of proportionality of the action taken in self-defence … concerns the relationship between that action and its purpose, namely … that of halting and repelling the attack … It would be mistaken, however, to think that there must be proportionality between the conduct constituting the armed attack and the opposing conduct. The action needed to halt and repulse the attack may well have to assume dimensions disproportionate to those of the attack suffered. … Its lawfulness cannot be measured except by its capacity for achieving the desired result. In fact, the requirements of the ‘necessity’ and ‘proportionality’ of the action taken in self-defence can simply be described as two sides of the same coin.Footnote 42
This viewpoint, particularly the claim that effectiveness in stopping an armed attack is determinant of proportionality,Footnote 43 has been addressed indirectly in other ICJ jurisprudence. In the 2003 Oil Platforms case (Iran v. USA), the Court concluded that:
As to the requirement of proportionality, the attack of 19 October 1987 might, had the Court found that it was necessary in response to the Sea Isle City incident as an armed attack committed by Iran, have been considered proportionate. In the case of the attacks of 18 April 1988, however, they were conceived and executed as part of a more extensive operation entitled ‘Operation Praying Mantis’. … As a response to the mining, by an unidentified agency, of a single United States warship, which was severely damaged but not sunk, and without loss of life, neither ‘Operation Praying Mantis’ as a whole, nor even that part of it that destroyed the Salman and Nasr [oil] platforms, can be regarded, in the circumstances of this case, as a proportionate use of force in self-defence.Footnote 44
Both the application and the precise threshold for the lawful use of force in self-defence remain uncertain.Footnote 45 Nonetheless, it is arguably the case that a state that uses an armed drone in a cross-border operation, which has not been consented to by the state on whose territory the ‘terrorist’ is located, may only legitimately claim it was acting in self-defence if the threat or use of force against it amounts to an armed attack.Footnote 46 A threat of an isolated, more limited ‘terrorist’ attack would therefore not be sufficient. This has potentially significant implications, in particular, for the use of armed drones by Israel on Palestinian territory. In any event, it would also appear, based on Article 51 of the UN Charter, that the use of an armed drone by a state against another or in another's territory purporting to be in self-defence must at least be immediately reported to the Security Council if it is to be lawful.Footnote 47 This is not known to have happened yet.Footnote 48
Drones and international humanitarian law
Potentially, the use of drones on the battlefield is relatively uncontroversial under jus in bello (without prejudice to jus ad bellum) because there may be scant practical difference between the use of a Cruise missile or an aerial bombardment and the use of a drone equipped with explosive weapons.Footnote 49 Indeed, according to the UN Special Rapporteur on extrajudicial, summary or arbitrary executions, although ‘in most circumstances targeted killings violate the right to life, in the exceptional circumstance of armed conflict, they may be legal’.Footnote 50 Whether or not the use of armed drones constitute aggression or legitimate self-defence, should they take place within a situation of armed conflict and fulfil the relevant nexus criteria (see below subsection on the nexus to the conflict) they will also be judged under applicable jus in bello, particularly IHL.Footnote 51 They will thus have to comply with, at a minimum, the IHL rules applicable to the conduct of hostilities, in particular those rules relating to precautions in attacks, distinction, and proportionality, and they must not employ weapons the use of which is unlawful under IHL. These rules are discussed in turn.
Precautions in attacks
There are direct links between respect for the rules on precautions in attacks and respect for other customary rules applicable to the conduct of hostilities, notably distinction (discrimination) and proportionality, as well as the prohibition on using means or methods of warfare that are of a nature to cause superfluous injury or unnecessary suffering. Most of the rules on precautions in attacks, which were codified in 1977 Additional Protocol I, are of a customary nature and are applicable in non-international armed conflict as well as in international armed conflict, according to the International Committee of the Red Cross (ICRC) study published in 2005. Central among the rules is the obligation to take ‘constant care’ in the conduct of military operations to ‘spare the civilian population, civilians, and civilian objects’. In this regard, ‘[a]ll feasible precautions must be taken to avoid, and in any event to minimise, incidental loss of civilian life, injury to civilians, and damage to civilian objects’.Footnote 52 Article 57 of the Protocol provides that those who plan or decide upon an attack shall ‘take all feasible precautions in the choice of means and methods of attack’.Footnote 53
For several reasons it could be argued that drone strikes might fulfil the requirements for precautions in attacks. First, a video feed from the drone can give ‘real-time’ eyes on the target so that the absence of civilians close to the target can be monitored until the last few minutes or even seconds.Footnote 54 Second, it appears that at least some of the targets of drone strikes are located using a tracking device that is presumably attached (or ‘painted’ on) to the vehicle, luggage, or equipment, or even potentially the person or one of the persons being targeted. Third, in certain cases (notably on Afghan soil), nearby military forces are also charged with monitoring the target. Fourth, other than the thermobaric variant of the Hellfire missile,Footnote 55 most of the missiles fired from drones are believed to have a smaller blast radius than other conventional munitions that might typically be deployed from a fighter jet. These factors do not eliminate the risk of civilian casualties, but they certainly represent feasible precautions that can minimize incidental loss of civilian life.Footnote 56
Significant failings have undeniably occurred, however, with one drone strike in Afghanistan in 2010 alone killing twenty-three Afghan civilians and wounding twelve others.Footnote 57 In May 2010, the US military released a report on the deaths, saying that ‘inaccurate and unprofessional’ reporting by Predator drone operators had led to the airstrike in February 2010 on the group of civilian men, women, and children.Footnote 58 The report said that four American officers, including a brigade and battalion commander, had been reprimanded, and that two junior officers had also been disciplined. General Stanley A. McChrystal, who apologized to Afghan President Hamid Karzai after the attack, announced a series of training measures intended to reduce the chances of similar events. General McChrystal also asked Air Force commanders to open an investigation into the Predator operators.Footnote 59
The question of how many civilians are killed in drone strikes is highly polarized.Footnote 60 It was reported in The New York Times in May 2012 that the Obama administration had embraced a method for counting civilian casualties that ‘in effect counts all military-age males in a strike zone as combatants … unless there is explicit intelligence posthumously proving them innocent’.Footnote 61 Seen in the light of these events, the ‘extraordinary claim’ in June 2011 by President Obama's top counterterrorism adviser, John O. Brennan, that there had not been ‘a single collateral death’ over the previous twelve months is of highly questionable accuracy.Footnote 62
The rule on distinction
With respect to the rule on distinction, which can be considered the most fundamental of all IHL rules, its application in an international armed conflict is far simpler than it is in an armed conflict of a non-international character. Use of drone strikes appears to have been confirmed in only two international armed conflicts to date, namely the USA and others against Afghanistan (the Taliban – as opposed to Al QaedaFootnote 63 – forces) in 2001–2002Footnote 64 and the one that pitted NATO member states' armed forces against Libya in 2011. It is, however, also likely that drone strikes were conducted in 2003–2004 during the attack against Iraq,Footnote 65 which formed part of the international armed conflict between the USA (and others) against the regime of Saddam Hussein.
These examples aside, it is clear that the overwhelming majority of drone strikes during armed conflict have occurred in conflicts that are non-international in character: by the USA and the UK in Afghanistan from June 2002;Footnote 66 and by the USA in Pakistan,Footnote 67 Somalia,Footnote 68 and Yemen.Footnote 69 In Iraq, unarmed drones are today being used by the US Department of State for surveillance purposes only;Footnote 70 armed drones were also used there in the past, with controversial effect.Footnote 71 In India, drones are employed to help Indian Special Forces to home in on Maoist fighters, but the UAVs they use are said to be unarmed.Footnote 72
Given these realities, the applicable rule on distinction – between lawful military objectives and civilians and civilian objects – is typically that which governs the conduct of hostilities in armed conflicts of a non-international character. Only lawful military targets, including civilians ‘participating directly in hostilities’, may lawfully be targeted by attacks, in accordance with the provisions of Common Article 3 to the four Geneva Conventions, as supplemented by customary international law (and, where applicable, Art. 13(3) of 1977 Additional Protocol II).Footnote 73
The ICRC's Interpretive Guidance on the Notion of Direct Participation in Hostilities under International Humanitarian Law is highly controversial in certain respects. No one appears to claim that IHL prohibits targeting the armed forces of a state that is party to a non-international armed conflict.Footnote 74 Far more controversial is the assertion that (military) members of organized armed groups that are a party to such a conflict likewise fulfil the requisite criteria on the basis of a claimed ‘continuous combat function’.Footnote 75 Those who exercise such a continuous combat function may, in principle, be targeted by attacks at any time (though this general permissiveness is subject to the rule on military necessity). As Alston observes:
the creation of CCF [continuous combat function] category is, de facto, a status determination that is questionable given the specific treaty language that limits direct participation to ‘for such time’ as opposed to ‘all the time.’ … Creation of the CCF category also raises the risk of erroneous targeting of someone who, for example, may have disengaged from his or her function.Footnote 76
A further challenge is how to identify – legally and practically – who such military members are. As the Interpretive Guidance published by the ICRC observes:
under IHL, the decisive criterion for individual membership in an organized armed group is whether a person assumes a continuous function for the group involving his or her direct participation in hostilities (hereafter: ‘continuous combat function’). … [This function] distinguishes members of the organized fighting forces of a non-State party from civilians who directly participate in hostilities on a merely spontaneous, sporadic, or unorganized basis, or who assume exclusively political, administrative or other non-combat functions.Footnote 77
Those who directly participate in hostilities on a merely spontaneous, sporadic, or unorganized basis may only lawfully be targeted while they so participate (although at other times they may of course be arrested by a law enforcement operation and charged under domestic law for offences committed). Those who assume exclusively political, administrative, or other non-combat functions may not be lawfully targeted unless and until they directly participate in hostilities, and only for such time as they undertake such acts.Footnote 78 In case of doubt as to his or her status, a person should be considered a civilian not directly participating in hostilities.Footnote 79
On this basis, using lethal force to target an Al Qaeda operative in Afghanistan who is engaged in planning, directing, or carrying out an attack in Afghanistan against, for example, US forces, would therefore be, a priori, lawful under the IHL rule of distinction. Targeting his son, his daughter, his wife, or wives would not be lawful, unless (and only for such time as) they were directly participating in hostilities.Footnote 80 The legality of an attack against the operative, where the attack was also expected to incidentally kill or injure civilians, would depend on a determination according to the rule of proportionality (see below subsection on proportionality in attacks).
Failing to make such a distinction during attack would render the attack unlawful and constitute evidence of a war crime.Footnote 81 In March 2012, the UK law firm Leigh Day & Co and the charity Reprieve launched an action against British foreign secretary William Hague on behalf of Noor Khan, whose father Malik Daud Khan was killed in a drone strike in Pakistan in 2011 ‘while presiding over a peaceful council of tribal elders’.Footnote 82
In 2009, it was reported in the media that the US Department of Defense's Joint Integrated Prioritized Target List – the Pentagon's roster of approved terrorist targets, containing 367 names – had been expanded to include some fifty Afghan drug lords suspected of giving money to help finance the Taliban.Footnote 83 Individuals engaged in the cultivation, distribution, and sale of narcotics are, a priori, criminals; however, even if they willingly or otherwise finance terrorism, they are not directly participating in hostilities in Afghanistan.Footnote 84 Targeting individual criminals with drone strikes would therefore be unlawful.
The rule of proportionality
Even if a target is a lawful military objective under IHL the question of proportionality arises and may either affect the selection of the means and methods of warfare that may lawfully be used, or even effectively prohibit an attack being launched. Violating the rule of proportionality is an indiscriminate attack according to 1977 Additional Protocol I.Footnote 85 The rule is not given voice in either Common Article 3 to the Geneva Conventions or 1977 Additional Protocol II, but is deemed to be a customary rule of IHL applicable not only in international armed conflict but also in armed conflicts of a non-international character. According to Rule 14 of the ICRC's study of customary international humanitarian law:
Launching an attack which may be expected to cause incidental loss of civilian life, injury to civilians, damage to civilian objects, or a combination thereof, which would be excessive in relation to the concrete and direct military advantage anticipated, is prohibited.
The question, of course, is what is ‘excessive’? In the ICRC-published commentary on Article 51(5) of the 1977 Additional Protocol I, from where the text setting out the rule on proportionality in attack originates, it is stated that:
Of course, the disproportion between losses and damages caused and the military advantages anticipated raises a delicate problem; in some situations there will be no room for doubt, while in other situations there may be reason for hesitation. In such situations the interests of the civilian population should prevail.Footnote 86
It is well known that different states have widely differing assessments of what is proportionate. Even close military allies, such as the UK and the USA, appear to differ materially on this issue. An instructive example occurred in Afghanistan in March 2011 when a UK Royal Air Force drone killed four Afghan civilians and injured two others in an attack against ‘insurgent leaders’ in Helmand province, the first confirmed operation in which a UK Reaper aircraft had been responsible for the death of civilians.Footnote 87 According to a press report, the UK Ministry of Defence spokesman said:
Any incident involving civilian casualties is a matter of deep regret and we take every possible measure to avoid such incidents. On 25 March a UK Reaper was tasked to engage and destroy two pick-up trucks. The strike resulted in the deaths of two insurgents and the destruction of a significant quantity of explosives being carried on the trucks. Sadly, four Afghan civilians were also killed and a further two Afghan civilians were injured. There are strict procedures, frequently updated in light of experience, intended to both minimise the risk of casualties occurring and to investigate any incidents that do happen.
An ISAF investigation was conducted to establish if any lessons could be learnt from the incident or if errors in operational procedures could be identified; the report noted that the UK Reaper's crews' actions had been in accordance with procedures and UK Rules of Engagement.Footnote 88
Nonetheless, a ‘source’, apparently from the UK Ministry of Defence, informed the British Guardian newspaper that the attack ‘would not have taken place if we had known that there were civilians in the vehicles as well’.Footnote 89 Thus, while the target (that is to say, individual insurgents in at least one of the pick-up trucks) would probably not have been unlawful under IHL, it seems that the UK would have considered it disproportionate to target the two insurgents had they had known that the civilians were present.
Contrast this example with the case of the Taliban leader, Baitullah Mehsud. On 23 June 2009, the CIA killed Khwaz Wali Mehsud, a mid-ranking Pakistan Taliban commander. They planned to use his body as ‘bait’ to target Baitullah Mehsud, who was expected to attend Khwaz Wali Mehsud's funeral. Up to 5,000 people attended the funeral, including not only Taliban fighters but many civilians. US drones struck again, killing up to eighty-three people. Forty-five of the dead were reportedly civilians, among them ten children and four tribal leaders. Such an attack raises very serious questions about respect for the prohibition on indiscriminate attacks. Baitullah Mehsud escaped unharmed, reportedly dying six weeks later, along with his wife, in another CIA attack.Footnote 90
The use of lawful weaponry
Customary law prohibits the use, whether in international or non-international armed conflicts, of inherently indiscriminate weapons, as well as of weapons that are of a nature to cause superfluous injury or unnecessary suffering.Footnote 91 In general, the Hellfire missiles typically fired from drones do not appear to violate this criterion.Footnote 92 As noted above, however, a cautionary note is warranted where potential use of thermobaric Hellfire missiles is concerned. Given their wide area effects and consequences for human beings, such thermobaric missiles demand further consideration under both general principles relating to weaponry.Footnote 93 Moreover, as drones are only platforms, other weapons can be – and are – used, which may fall foul of the rules prohibiting the use of unlawful weapons in armed conflict.
The nexus to the conflict
Are the strikes in Pakistan, specifically those against Al Qaeda suspects, to be considered legal conduct of hostilities within the armed conflict in Afghanistan?Footnote 94 In remarks online on 31 January 2012, President Obama said that the drone strikes in Pakistan, which are carried out by the CIA rather than the military,Footnote 95 are a ‘targeted, focused effort at the people who are on a list of active terrorists’ and that the USA was not just ‘sending in a whole bunch of strikes willy-nilly’ but targeting ‘Al Qaeda suspects who are up in very tough terrain along the border between Afghanistan and Pakistan’.Footnote 96 A ‘terrorist’ is not, however, necessarily someone who is engaged in an armed conflict (let alone the even further removed case of drug lords noted above). There must be a clear nexus to an armed conflict with a clearly defined non-state party, not an ill-defined, globalized ‘war against terror’, especially since the current US administration has sought to distance itself from such rhetoric.Footnote 97 As Melzer has noted:
Whether or not a group is involved in hostilities does not only depend on whether it resorts to organized armed violence temporally and geographically coinciding with a situation of armed conflict, but also on whether such violence is designed to support one of the belligerents against another (belligerent nexus).Footnote 98
According to the US Attorney General, Eric Holder, who addressed the issue of drone strikes in a speech in March 2012, the US government's ‘legal authority is not limited to the battlefields in Afghanistan’. Mr Holder said there were circumstances under which ‘an operation using lethal force in a foreign country, targeted against a US citizen who is a senior operational leader of Al Qaeda or associated forces, and who is actively engaged in planning to kill Americans, would be lawful’.Footnote 99 Such circumstances included that a thorough review had determined the individual posed ‘an imminent threat of violent attack against the United States’, that ‘capture is not feasible’, and the ‘operation would be conducted in a manner consistent with applicable law of war principles’.Footnote 100
While the limiting of legality of targeted killings to senior operational leaders of Al Qaeda or associated forces who pose ‘an imminent threat of violent attack against the United States’ might be welcome as it suggests that unless the threat of violent attack is ‘imminent’, an attack will not be authorized, it still raises a series of questions. First, what constitutes an ‘imminent’ threat? Second, many of those killed in drone strikes in Pakistan are not senior leaders but mid- or low-level fighters. Quid the legality of these strikes? Or do the criteria only restrict drone strikes when it concerns a US citizen? Is it ‘open season’ on foreign nationals?Footnote 101 Third, is an attack against US forces in Afghanistan by fighters based in Pakistan deemed a terrorist attack by the US government? Although the definition of terrorism remains highly controversial, many would argue that it is the targeting of civilians, not members of a state's armed forces, that is one of the defining characteristics of terrorism,Footnote 102 along with an associated attempt to influence government policy on one or more issues. This is clearly not, however, the US government's understanding of the term ‘terrorism’.
And, again, the Attorney General's statement does not address the issue of whether such strikes form part of an armed conflict: an oral commitment to conduct an operation ‘in a manner consistent with applicable law of war principles’ does not mean that IHL is applicable under international law. The US Supreme Court, in Hamdan v. Rumsfeld, rejected the assertion that the conflict was a global war against Al Qaeda to which the Geneva Conventions did not apply, and specifically determined that Common Article 3 to the Geneva Conventions applied to Salim Ahmed Hamdan, a former bodyguard and driver of Osama bin Laden, an individual who was captured by US military forces inside Afghanistan in November 2001.Footnote 103 This judgment does not mean that anyone – wherever he (or she) may be in the world – affiliated to Al Qaeda is drawn into an armed conflict of a non-international character against the USA as a person participating directly in hostilities by virtue of espousal of, or even indirect support for, a violent ideology.Footnote 104
Drone strikes and international human rights law
The application and impact of IHL on drone strikes in a situation of armed conflict having been reviewed above, this section looks at the implications of international human rights law for the use of armed drones. The first targeted killing using a drone strike outside a theatre of armed conflict is believed to have been the killing of six alleged Al Qaeda members, including Qaed Senyan al-Harithi, also known as Abu Ali, who was the suspected mastermind of the bombing of the USS Cole in October 2000.Footnote 105 The six were killed on 3 November 2002 in Yemen when either one or two Hellfire missilesFootnote 106 launched from a drone controlled by the US Central Intelligence Agency (CIA) destroyed the jeep in which they were travelling in the northern Yemeni province of Marib, about 160 kilometres east of Sana'a.Footnote 107 Since then, targeted killings using drones have become a regular occurrence in Pakistan and, albeit to a lesser extent, in Yemen as well as in other countries.Footnote 108 The September 2011 killing, by a CIA drone, in Yemen of Anwar al-Awlaki, a radical Muslim cleric of Yemeni descent, was particularly controversial as he was a US citizen.Footnote 109 After earlier failed drone strikes against him, his family had launched a legal challenge seeking to prevent the USA from executing one of its citizens without any judicial process.Footnote 110
The first subsection below discusses how human rights law regulates the use of force outside armed conflict in a ‘law enforcement’ situation, while the second looks at its role and consequences – actual and potential – within armed conflict as a constituent of jus in bello alongside IHL.
Application of human rights law to law enforcement
Under international human rights law two important principles govern all use of force in a law enforcement setting: necessity and proportionality. Although these terms have been used in the context of both jus ad bellum and IHL, their precise meaning in the context of human rights law is markedly different. As Alston has stated: ‘A State killing is legal only if it is required to protect life (making lethal force proportionate) and there is no other means, such as capture or nonlethal incapacitation, of preventing that threat to life (making lethal force necessary)’.Footnote 111 A further requirement is that the threat to life which the use of lethal force is seeking to forestall must be imminent.Footnote 112 Thus, in its approach to regulating the intentional use of lethal force, international human rights law generally embraces the standards laid down in the 1990 Basic Principles on the Use of Force and Firearms by Law Enforcement Officials (the ‘Basic Principles’).Footnote 113 According to the final sentence of Basic Principle 9: ‘In any event, intentional lethal use of firearms may only be made when strictly unavoidable in order to protect life’.Footnote 114
This general position is, however, subject to two caveats. First, the Basic Principles were not designed to regulate acts by armed forces in a situation of armed conflict, which remain under the purview of jus in bello. Second, the threshold for the intentional lethal use of force has been set less restrictively by domestic US jurisprudence (relating to police powers) and similarly interpreted more permissively by the Inter-American Commission on Human Rights (with respect to counterterrorism operations).Footnote 115 In Tennessee v. Garner,Footnote 116 the US Supreme Court stated that:
Where the officer has probable cause to believe that the suspect poses a threat of serious physical harm, either to the officer or to others, it is not constitutionally unreasonable to prevent escape by using deadly force. Thus, if the suspect threatens the officer with a weapon or there is probable cause to believe that he has committed a crime involving the infliction or threatened infliction of serious physical harm, deadly force may be used if necessary to prevent escape, and if, where feasible, some warning has been given.Footnote 117
Other nations, including Australia and the UK, support the higher standard as set out in the Basic Principles. For example, the UK has a shoot-to-kill policy for suspected suicide bombers, but which clearly meets that higher standard because a suicide bomber not only threatens death, but also is likely to meet the criterion of imminence that is an integral element accompanying the level of threat. Following the July 2005 killing by Metropolitan Police officers of an unarmed youth, Jean Charles de Menezes, wrongly suspected to be a suicide bomber and shot seven times at point-blank range,Footnote 118 Lord Stevens, the former Metropolitan Police Commissioner, made public – in a British tabloid newspaper – a policy that had been adopted when he was in charge in 2002.Footnote 119 He told that British newspaper that the teams he sent to Israel and other countriesFootnote 120 hit by suicide bombers after the 11 September 2001 attacks in the USA had learned a ‘terrible truth’, that the only way to stop a suicide bomber was to ‘destroy his brain instantly, utterly’. Previously, officers had fired at the offender's body, ‘usually two shots, to disable and overwhelm’.Footnote 121 Sir Ian Blair, who was Commissioner in 2005, stated that there was ‘no point’ in shooting a suspect in the chest as that is where a bomb would most likely be and it would detonate.Footnote 122
The question of imminence is extremely important to the issue of drone strikes, especially given the risk of subjectivity and lack of transparency as to who is on the US list of those designated for elimination.Footnote 123 The speech by Attorney General Holder in March 2012 appeared to seek to marry two different legal regimes – one applicable to a law enforcement paradigm and the other applicable to armed conflict – when he claimed that authorization for the use of a drone strike against a US citizen would require ‘a thorough review’ that had determined the individual posed ‘an imminent threat of violent attack against the United States’ and that ‘capture is not feasible’. In 2010, Koh stated that:
[it] is the considered view of this Administration – and it has certainly been my experience during my time as Legal Adviser – that US targeting practices, including lethal operations conducted with the use of unmanned aerial vehicles, comply with all applicable law, including the laws of war.Footnote 124
In May 2012, The New York Times reported on the existence of ‘Terror Tuesdays’, when the US President would decide who would be killed by the USA, typically through drone strikes:
This was the enemy, served up in the latest chart from the intelligence agencies: 15 Qaeda suspects in Yemen with Western ties. The mug shots and brief biographies resembled a high school yearbook layout. Several were Americans. Two were teenagers, including a girl who looked even younger than her 17 years.Footnote 125
Given the significant constraints on the intentional use of lethal force under international human rights law, Alston concludes that: ‘Outside the context of armed conflict, the use of drones for targeted killing is almost never likely to be legal. A targeted drone killing in a state's own territory, over which the State has control, would be very unlikely to meet human rights law limitations on the use of lethal force’. Furthermore, outside a state's own territory,
there are very few situations outside the context of active hostilities in which the test for anticipatory self-defence … would be met. … In addition, drone killing of anyone other than the target (family members or others in the vicinity, for example) would be an arbitrary deprivation of life under human rights law and could result in state responsibility and individual criminal liability.Footnote 126
For Lubell, for example, the killing of al-Harithi in Yemen in 2002 was unlawful on the basis that it violated the right to life as set out in the 1966 Covenant on Civil and Political Rights.Footnote 127
Application of applicable international law within and linked to armed conflict
Aside from, and in addition to, any determination under jus ad bellum of the legality of the use of force in another state, international human rights law will be the primary source of international law determining the legality of the use of drones outside a situation of armed conflict. Within a situation of armed conflict and with respect to acts that represent the requisite nexus, at least non-derogable rights will continue to apply fully, while others may be subject to derogation to the extent ‘strictly required by the exigencies of the situation’.Footnote 128 Since armed drone strikes are most obviously a threat to life even though they may directly or indirectly affect numerous other human rights, analysis will focus on this ‘supreme’ right (in the words of the UN Human Rights Committee).Footnote 129
Applicability of human rights law in armed conflicts
In an oft-cited dictum pertaining to the right to life as set out in 1966 Covenant on Civil and Political Rights, the ICJ opined in 1996 that:
the protection of the International Covenant on Civil and Political Rights does not cease in times of war, except by operation of Article 4 of the Covenant whereby certain provisions may be derogated from in a time of national emergency. Respect for the right to life is not, however, such a provision. In principle, the right not arbitrarily to be deprived of one's life applies also in hostilities. The test of what is an arbitrary deprivation of life, however, then falls to be determined by the applicable lex specialis, namely, the law applicable in armed conflict which is designed to regulate the conduct of hostilities. Thus whether a particular loss of life, through the use of a certain weapon in warfare, is to be considered an arbitrary deprivation of life contrary to Article 6 of the Covenant, can only be decided by reference to the law applicable in armed conflict and not deduced from the terms of the Covenant itself.Footnote 130
Several states argued, unsuccessfully, before the Court that the Covenant – and indeed human rights in general – was not applicable in a situation of armed conflict. This position is rarely heard today, and has been generally discredited.Footnote 131
Relationship between human rights law and international humanitarian law
In contrast, the Court's assertion that whether the right to life has been violated depends on a renvoi to the law applicable in armed conflict as lex specialis Footnote 132 still attracts widespread support. On a superficial reading, this would appear to constitute total deference to IHL. There are, though, a number of reasons for questioning such an assertion. As Christian Tomuschat has noted,Footnote 133 the Court's statement was ‘somewhat short-sighted’Footnote 134 given that in the issue before it, the legality of the threat or use of nuclear weapons, it was unable to ‘conclude definitively’ based on IHL interpretation whether such threat or use ‘would be lawful or unlawful in an extreme circumstance of self-defence’.Footnote 135 Second, as he and others have observed, the Court's appraisal of the mutual relationship between IHL and human rights law has been modified in subsequent decisions,Footnote 136 notably the Advisory Opinion in the Wall case (2004)Footnote 137 and the decision in the Armed Activities on the Territory of the Congo case (2005).Footnote 138 According to Alston, since both IHL and human rights law apply in the context of armed conflict,
whether a particular killing is legal is determined by the applicable lex specialis. … To the extent that IHL does not provide a rule, or the rule is unclear and its meaning cannot be ascertained from the guidance offered by IHL principles, it is appropriate to draw guidance from human rights law.Footnote 139
Others, including this author, would go even further. Milanović, for example, notes the omission of a reference to IHL as lex specialis in the ICJ judgment in the 2005 Congo case, compared with its Advisory Opinions in the Wall case and the Nuclear Weapons case, and expresses the hope that this was intentional.Footnote 140 In a 2011 European Journal of International Law blog, he stated:
A bolder approach to the joint application of IHL and IHRL [international human rights law] would ask whether there are killings which do comply with IHL but are still arbitrary in terms of IHRL. Can, in other words, IHRL during armed conflict impose additional requirements for the lawfulness of a killing to those of IHL? And can these requirements, while more stringent than those of IHL, still be somewhat less stringent than those set out in human rights jurisprudence developed in and for times of normalcy …? … I think all these questions can be answered with a cautious ‘yes’.Footnote 141
Indeed, in its Nuclear Weapons Advisory Opinion, the Court had made it clear that the law applicable in armed conflict (jus in bello) was not limited to IHL.Footnote 142 Further evidence that it could be overly simplistic to interpret the right to life in a situation of armed conflict merely through the lens of compliance with IHL comes from the meaning of ‘arbitrarily deprive’. With respect to the 1966 Covenant on Civil and Political Rights, the term is said to contain ‘elements of unlawfulness and injustice, as well as of capriciousness and unreasonableness’.Footnote 143
There is a clear limit to this approach, however. While human rights law has much to bring to the IHL table in terms of limiting violence and promoting humanity (for instance, by contributing to a greater understanding of what constitutes in practical terms ‘the principles of humanity’ and the ‘dictates of public conscience’ in the application of the Martens clause), it is not being suggested here that a weapon that is generally lawful under IHL is somehow generally rendered unlawful by human rights law. Lubell, for example, indicates that the laws on the selection of weaponry are rightly addressed by IHL without interference from human rights law.Footnote 144 (In fact, it could even be argued that such interference would run the risk of weakening IHL, given that tear gas and expanding bullets, outlawed under IHL as a method and a means of warfare, respectively, might be somehow rendered legitimate as they can be used for law enforcement in compliance with international human rights law.)
Nonetheless, an increased, and increasing, influence of human rights law on the content of jus in bello, an area formerly considered the domaine réservé of IHL, should be seen not as a threat but as a necessary counterbalance to the more aggressive acts of certain states in response to, what they espouse as, a new legal paradigm in the post-9/11 world.Footnote 145 Restraint is not a sign of weakness – it is a sign of strength. With respect to drones, it is said that the CIA refused to deploy the Predator for anything other than surveillance prior to 9/11. The week before the Al Qaeda attacks against the US, the then-Director of the CIA, George Tenet, is reported to have remarked, referring to drones, that it would be ‘a terrible mistake’ for the ‘Director of Central Intelligence to fire a weapon like this’.Footnote 146 How prophetic this statement may prove to be.
Conclusion
Drones can enable states to carry out targeted killings efficiently, at relatively little cost, and at minimal risk. In the Corfu Channel case,Footnote 147 the ICJ stated that:
the alleged right of intervention as the manifestation of a policy of force, such as has, in the past, given rise to most serious abuses and such as cannot, whatever be the present defects in international organization, find a place in international law. Intervention is perhaps still less admissible in the particular form it would take here; for, from the nature of things, it would be reserved for the most powerful States, and might easily lead to perverting the administration of international justice itself.Footnote 148
Too often, targeted killings by states, whether using drones or other means, look rather like crossing names off a Mafia hit list. Indeed, as Melzer has observed: ‘In the final analysis, … measured by the moral standards common to most societies, even targeted killings carried out within the framework of the present legal order often have traits that are more readily associated with criminal behaviour than with acceptable Government policy’.Footnote 149 And in the words of a former CIA lawyer: ‘The government's power to kill must be carefully controlled – or it could turn into a tyranny worse than terrorism’.Footnote 150
Such control means international legal responsibility for unlawful drone strikes, both at the level of the state and the individual. But who is to be held criminally responsible when civilians are killed either in violation of IHL rules of distinction or proportionality or in violation of fundamental human rights? The operator of the drone? The ‘spotters’ on the ground (if any)? Those who designate the target as a military objective (who may be paid informants)? The lawyer who authorizes the strike? All of the above? If the strike is unlawful, could it be an example of a joint criminal enterprise under international criminal law, or have one or more of the above aided or abetted an international crime?
Of even greater concern is the prospect of fully autonomous drones making targeting decisions based on a series of programmed vectors, potentially without any human control.Footnote 151 Who is then to be held responsible? The manufacturer of the drone? The software programmer? For the moment, there are far more questions than answers.
Moreover, it is only a matter of time before non-state armed groups develop or procure drone technologyFootnote 152 (or hack into the operation of a state-controlled drone and assume control).Footnote 153 Will not such groups be seeking actively to level the killing field? As a Senior Fellow with the Brookings Institute warned in 2011:
To believe that drones will remain the exclusive province of responsible nations is to disregard the long history of weapons technology. It is only a matter of time before rogue groups or nations hostile to the United States are able to build or acquire their own drones and to use them to launch attacks on our soil or on our soldiers abroad.Footnote 154
Pandora's box has been opened, but undoubtedly even nastier surprises are yet to emerge.
