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The Oxford Handbook of the Use of Force in International Law edited by Weller, Marc (1st January 2015)

Part VI Emerging Areas?, Ch.51 Remotely Piloted Warfare as a Challenge to the Jus Ad Bellum

Jordan J. Paust

From: The Oxford Handbook of the Use of Force in International Law

Edited By: Marc Weller

From: Oxford Public International Law (http://opil.ouplaw.com). (c) Oxford University Press, 2015. All Rights Reserved. Subscriber: null; date: 19 June 2019

Subject(s):
UN Charter — Self-defence — Armed forces — Weapons, nuclear — Armed attack — Customary international law — Opinio juris

(p. 1095) Chapter 51  Remotely Piloted Warfare as a Challenge to the Jus Ad Bellum

I.  Introduction

The phrase ‘remotely piloted warfare’ has several potential meanings depending on what is covered by the phrase ‘remotely piloted’1 and by the (p. 1096) word ‘warfare’,2 These, in turn, can be related to phrases in the UN Charter that are relevant to the overall focus of this volume, such as the use of ‘armed force…in the common interest’,3 ‘the threat or use of force against’ territorial integrity or political independence,4 Security Council-authorized ‘enforcement action’,5 ‘regional action’ authorized by an appropriate regional organization,6 and ‘self-defense if an armed attack occurs’.7

Although use of remotely piloted armed aerial vehicles in combat by the US and the North Atlantic Treaty Organization (NATO) has been relatively new during the last two decades, various present and foreseeable uses of remotely piloted methods and means of armed force and warfare do not appear to necessitate any change in UN Charter precepts regarding the use of force by state and non-state actors. The fact that they will evolve in several ways and become increasingly accessible to states and non-state actors, however, may result in increased permissible use of armed force by states with respect to self-defence, collective self-defence, self-determination assistance,8 regional action, and enforcement action authorized by the UN Security Council. Their increased use as platforms for armed force during war or relative peace and as methods and means of self-defence has already noticeably resulted in a greater potential for compliance with principles of reasonably necessity, distinction in targeting, and proportionality,9 which are (p. 1097) general principles that are also relevant to permissibility of the use of armed force under the UN Charter and relevant customary international law or the jus ad bellum.10 However, future application of these principles in connection with use of remotely piloted attacks, self-defence, and warfare might result in challenges regarding interpretation and application around the edges of normative meaning with respect to Article 2(4) of the UN Charter and permissible self-defence under Article 51 of the Charter, especially for those who prefer that there should be (p. 1098) limitations of the inherent right of self-defence in terms of the character, gravity, area, and scale of state and non-state armed attacks,11 whether or not the attackers use robotic vehicles.

II.  The ‘Remotely Piloted’ Phenomenon

Drones are the current primary example of remotely piloted aerial vehicles that are used during war and self-defence,12 what some term unmanned aerial vehicles (UAVs) even though they are not fully automated and are flown by humans situated outside the aerial vehicles. Drones were first used for aerial intelligence, surveillance, and reconnaissance during war.13 They are also used for intelligence, surveillance, investigation, and related purposes during times of relative peace within a country,14(p. 1099) along its borders,15 and in other countries and over the high seas.16 For example, it has been reported that the US Central Intelligence Agency (CIA) used an RQ-170 Sentinel drone in Iranian airspace for surveillance of possible nuclear weapons production activities by Iran and that the drone may have been taken down or flown and landed through a cyber-attack, jamming, or hijacked control of the drone.17 In Afghanistan, soldiers have flown model airplanes over areas that they were about to enter in order to provide needed intelligence. In the future, ‘observant machines’ that can recognize, observe, and analyse human beings, especially through facial observation and analysis, can be ‘Mounted on small robots or drones’ and used for law enforcement, national security, and military operations.18

III.  Possible Challenges to Compliance with Basic Legal Principles that Limit Violence

As noted, drones have been used relatively recently in human history as platforms on which various types of weapons have been utilized during war and measures of self-defence. They can come in various sizes,19 and in the future some will predictably be the size of a dragonfly. Some drones and other robotics are also likely to use increasingly sophisticated computerized forms of intelligence-gathering and analysis for decision-making with respect to identification and engagement of targets during war and self-defence, perhaps even with a completely autonomous (p. 1100) decisional, learning, and operational capability.20 Are there identifiable challenges posed by the foreseeable development and increasing availability and use of drones and other robotics? Will their increased use require changes in the laws of war or the jus ad bellum, especially with respect to the need to adhere to basic legal principles that limit violence and its effects?

Presently, it is not generally expected that use of drones for targeting during war will require a change in the laws of war,21 and it is not generally expected that related use for targeting during permissible measures of self-defence will require a change in the law of self-defence.22 Nonetheless, their use has raised questions with respect to the ease of going to war,23 the ease of killing human beings, and application of (p. 1101) general principles that condition permissible use of force under the laws of war and jus ad bellum.

Moreover, there are at least two predictable developments in drone technology that raise concerns whether drones will be sufficiently controlled and permit compliance with general principles of necessity, distinction, and proportionality. First, there is concern that some drones will become completely autonomous and will be used to hunt and quickly eliminate human beings and objects within the matrix of programmed targets. Presently, drones used for targeting during war and self-defence are operated by human beings, and there are often others who can participate in decisions concerning target identification and whether to engage a particular target. Drones often have the capability to fly over an area for hours, allowing nuanced human choice with respect to all features of context,24 including those concerning identification of the target; the importance of the target; whether equally effective alternative methods of targeting or capture exist; the presence, proximity, and number of civilians who are not targetable; whether some civilians are voluntary or coerced human shields; the precision in targeting that can obtain; and foreseeable consequences with respect to civilian death, injury, or suffering.25

Some foresee a growing use of on-board computers to locate targets, provide valuable contextual input, and coordinate with other drones and aircraft, but assume that human beings will still make needed choices concerning proper application of the principles of distinction and proportionality and whether a target should even be engaged under the circumstances.26 Others foresee a problematic future use of (p. 1102) drones that are completely autonomous and, if they do not kill and destroy needlessly because of computer glitches,27 they might kill and destroy without adequate consideration of all relevant features of context despite possible increased sophistication in their programming. Their use would surely be ‘smarter’ than use of dumb spring-guns,28 but not without foreseeably deleterious consequences. In fact, some systems can be placed in an autonomous mode by a human decision-maker and then hunt for human or material targets in a defensive or offensive manner.29 Depending on their capabilities, smart autonomous hunting drones and other hunting robots might be blind with respect to the need to comply with customary principles of distinction and proportionality. When released in an area, they might hunt all humans or all relevant objects indiscriminately, and they might cross borders30 in ways that violate UN Charter precepts.

One can envision use of fully autonomous aerial, land, and naval mines that do not stay in one place and actually hunt without human supervision. Aerial and naval hunting mines might be used for defensive purposes in an area, but if fully automated they might destroy civilian and neutral governmental aircraft and vessels in violation of international law. If the aircraft or vessels are foreign registered or foreign flagged, their destruction would be the equivalent of destruction of foreign territory31 and could constitute a use of force in violation of the Charter.32 Hunting drones might not have the capacity to distinguish between aircraft that have been warned away but keep coming and aircraft that have turned away and are no longer reasonably expected to be engaged in an attack that can trigger the right of self-defence.33

With respect to mines, the International Court of Justice (ICJ) has recognized that the laying of mines in the territory of another state can constitute a breach of customary international law prohibiting the use of armed force against another state34 and that ‘the mining of a single military vessel’ might trigger the inherent right of self-defence.35 One remedy with respect to errant drones and mines that are known to be crossing a border or about to unlawfully attack foreign aircraft or (p. 1103) vessels could involve use of a human override capability to destroy or regain control over an errant drone or mine. An ability to turn off naval and land-based mines would be useful, for example to avoid damage to and destruction of hospital and neutral ships and ambulances.

Secondly, it has been reported that research ‘is headed away from single drones and towards a co-ordinated team or swarm of vehicles with a specified mission and location… a swarm of robots’, and that ‘inevitably there will be more autonomy; the robots will be required to make more decisions.’36 It is also foreseeable that with respect to swarms, a human can provide the initial order to a swarm, but ‘drones in the armed swarm would work out between them which element would enact an attack order.’37 Quite possibly, use of a swarm might pose greater danger with respect to computer glitches and the need for nuanced decision-making with respect to identification and engagement of particular targets. Nonetheless, the swarm can prove to be valuable with respect to some forms of lawful uses of offensive and defensive force. Basic legal norms do not need to be changed, but efforts should be made to assure the existence of adequate computerized and human controls and the development of rules of engagement (ROE) to restrain their actual use. Wanton and reckless disregard of consequences can lead to criminal and civil sanctions,38 but these can occur with respect to misuse of any weapons system.

IV.  Drone Targeting and Charter-Based Precepts

A.  Challenges to Charter-Based Purposes and Principles

1.  Force in the common interest

Among general issues identified is concern whether increased availability and use of drones will lead to an increase in the use of armed force by states, either unilaterally or in cooperation with others.39 If the government of a particular state uses drones to target enemies in war and in self-defence, there can be a lessening of (p. 1104) the loss of lives of its citizens and those of other countries, but will this outcome result in an increased use of armed force by states? Actually, the decision whether to engage in permissible war will likely be far more complex and a state’s choice, for example, to merely use drones will not be determinative. Perhaps some states with drone capability will be tempted to use force more readily against weaker enemies, but this remains uncertain.

If drones make it easier for a state to use force or go to war, this will clearly have an impact on a stated purpose of the peoples of the UN ‘to save succeeding generations from the scourge of war’ and to assure ‘that armed force shall not be used, save in the common interest.’40 It may or may not also impact negatively with respect to decisions of regional organizations to authorize the use of armed force as part of lawful ‘regional action’ under Article 52 of the Charter or decisions of the Security Council to authorize the use of armed force as part of lawful ‘enforcement action’ under Article 42 of the Charter. However, at least choice-making by regional organizations and the Security Council will avoid problems connected with unilateralist decision-making and, on balance in specific contexts, might generally serve the common interest despite the fact that forms of violence are being authorized. Moreover, to be lawful measures of violence, regional organizations and the Security Council must make their decisions in accordance with the purposes and principles of the UN Charter.41

2.  Force and Article 2(4)

It may also be the case that some who prefer that minor uses of force across borders should not be of sufficient gravity, expanse, and duration to constitute a use of armed force within the meaning of Article 2(4) of the Charter will be prone to conclude that intentional, short-lived, and precise targeting by a drone across a border will not constitute a violation of Article 2(4). If their viewpoint is generally preferred, this type of conclusion might lead to an increased use of drones for precise cross-border targetings even when targetings are not justifiable as measures of self-defence. With respect to errant hunting, drones that cross into the territory of another state and impermissibly target human beings or objects or that impermissibly destroy civilian and governmental aircraft or vessels, would most likely not come under the first two prohibitions addressed in Article 2(4) because, even if such outcomes were foreseeable or the result of wanton disregard, there (p. 1105) would not be an intentional use of armed force ‘against’ the territorial integrity or political independence of another state or the equivalent of its territory—assuming that the word ‘against’ requires an intent to do so. Nonetheless, the third (and only other42) prohibition addressed in Article 2(4) might not rest on a need for intended outcomes. The third prohibition encompasses the use of force ‘in any other manner inconsistent with the Purposes of the United Nations.’43 The phrase ‘inconsistent with’ necessarily requires contextual and policy-serving inquiry and may not demand intent to produce such an outcome. Since the purposes of the UN include the need to assure that armed force not be used save in the common interest and the need to serve peace, security, self-determination, and human rights,44 it may be that the decision to deploy hunter drones in wanton or reckless disregard of foreseeable consequences that are inconsistent with the purposes of the UN will constitute a prohibited use of armed force under the third provision in Article 2(4).

3.  Force in self-defence

One can assume that use of drones by states in self-defence outside the context of war will not increase the frequency of violent measures of self-defence because permissibility under Article 51 of the Charter is limited by the need for an ‘armed attack’ to have taken place or for a process of armed attacks to continue,45 as well as the need for compliance with general principles of reasonable necessity, distinction, and proportionality.46 Nonetheless, an increased availability of ‘weaponized’ drones for non-state actors (especially those bent on achieving outcomes of terror) might (p. 1106) lead to an increased use of non-state actor armed attacks on states, their embassies abroad, and their military personnel and other nationals abroad that trigger the inherent right of self-defence,47 but this is difficult to predict given the fact that over the last few decades several non-state actors have engaged in such armed attacks without the use of drones and it is generally expected that so-called asymmetric warfare and violence will increase in any event. However, some who prefer that an ‘armed attack’ be of significant gravity48 before it triggers the inherent right of self-defence may have to change their preference as limited forms of non-state actor armed attacks increase and in reality require immediate and precise responsive uses of force that can be achieved through use of drones, whether or not the non-state actor attacks are terroristic in purpose and effect or amount to measures of asymmetric war across national borders. Restrictivist interpretations can encourage non-state actors to attack across borders and provide functional safe havens.

A hypothetical from another publication demonstrates the point that even a few relatively low-level rocket attacks by non-state actors across borders will likely be considered by states to constitute armed attacks even if others debate whether they are of significant ‘gravity’ and effect. For real-world decision-makers who see their fellow nationals being killed, injured, and terrorized, a supposed gravity limitation will be simply unavailing.

Consider the circumstance where a non-state terrorist group acquires rockets capable of striking short-range targets and starts firing them from Mexico (without the consent of the Government of Mexico or prior foreseeability) into Fort Bliss, a U.S. military base near El Paso, Texas. Must the United States actually obtain a special express consent of the Mexican Government or already be engaged in a war with the terrorist group (if that is even possible) before resorting to a selective use of force in self-defense to silence the terrorist attacks on U.S. military personnel and other U.S. nationals? I doubt that any state under such a process of armed attack would wait while the rocket attacks continue or expect that (p. 1107) under international law it must wait to engage in selective self-defense against the attackers. Furthermore, I doubt that any state would expect that it cannot engage in measures of self-defense to stop such rocket attacks if it had not been and cannot be at war with non-state terrorist attackers or that it cannot take such defensive measures if it is not otherwise engaged in a relevant armed conflict.

Certainly the President of the US would try to communicate as soon as possible with the President of Mexico and others concerning what is happening and the fact that the US is not attacking Mexico, but the US President would not have to wait for a formal response while rockets are raining down on US soldiers. Additionally, although it would be polite, the US would not have to warn Mexican authorities before engaging in selective measures of self-defence to stop continuing attacks. Under various circumstances, a warning can be impracticable, futile, and/or create complications threatening the success of a self-defence response, especially in other contexts if a special operations unit is being used for reconnaissance or to carry out the self-defence action.49

B.  Some Present Applications and Issues Regarding Compliance

Weaponized drones have been used during war and otherwise in self-defence. Has their use necessarily resulted in violations of the UN Charter, as some suggest?50 Issues have arisen concerning application of various articles of the Charter to actual drone targetings, but it is apparent that whether or not there has been a use of drones should not be critical to informed and policy-serving inquiry—especially since there are and will be various types of drones that might use various types of weapons.

Use of drones for targeting in self-defence (whether or not such occurs also in the context of war) has been controversial for some but has also led to reaffirmation of several important aspects of permissible self-defence. For example, the vast majority of text-writers have affirmed that non-state actor armed attacks can trigger the right of self-defence addressed in Article 51 of the Charter even if selective responsive force directed against a non-state actor occurs within a foreign country,51 and (p. 1108) nothing in the language of Article 51 restricts the right to engage in self-defence to circumstances of armed attacks by a state.52 Moreover, nothing in the language of the Charter requires a conclusion lacking in common sense that a state being attacked can only defend itself within its own borders. General patterns of pre-Charter and post-Charter practice and general patterns of opinio juris affirm these points as well as the fact that a state being attacked does not need special express consent of the state from which non-state actor armed attacks emanate and on whose territory a self-defence drone targeting takes place against the non-state actor.53 Additionally, it would be demonstrably incorrect to claim that a state has no right to defend itself outside its own territory absent (1) attribution or imputation of non-state actor attacks to the foreign state when the foreign state is in control of non-state actor attacks,54 or (2) the existence of a relevant international or non-international armed conflict.55 Moreover, the inherent right of self-defence in case of an armed attack is not limited to a circumstance where the state from whose territory a non-state actor armed attack emanates is unwilling or unable to control its territory.56 Conversely, the mere existence of such a circumstance does not justify the use of armed force in a foreign state without its consent if, for example, the right of self-defence has not been triggered because there has been no armed attack or process of armed attacks.

As noted in another publication, with respect to the need to serve various policies at stake in the context of continual non-state actor armed attacks, including peace, (p. 1109) security, human rights, and effective opposition to international crime, it is important to note that state sovereignty:

is not absolute under international law or impervious to its reach, territorial integrity of the state is merely one of the values preferred in the U.N. Charter, and permissible measures of self-defense under Article 51 of the Charter that are reasonably necessary and proportionate against actual armed violence must necessarily override the general impermissibility that attaches to armed intervention.57

One should also note that the self-defence paradigm is different from both a mere law of war paradigm applicable during armed conflict and a law enforcement paradigm, and self-defence targetings and captures can occur with respect to those who are direct participants in armed attacks (DPAAs) whether or not an armed conflict exists that would also allow the targeting and capture of persons who are combatants, civilians who are direct participants in hostilities (DPHs), or civilians who are unprivileged fighters engaged in a continuous combat function.58 Clearly, selective use of armed force as part of permissible self-defence is not simplistically ‘law enforcement’ or limited by what would only be authorized during law enforcement, whether or not lawful use of force in self-defence is undertaken in time of war or relative peace.

V.  Conclusion

Use of remotely piloted and other robotics during war and otherwise outside the context of war during permissible measures of self-defence is likely to increase, and their use by non-state actors is foreseeable. Such uses will pose challenges for some regarding interpretation of Articles 2(4) and 51 of the UN Charter and application of underlying general principles, but it is generally expected that increased use will not require changes in the laws of war or the law of self-defence. Yet, use of autonomous robotics can lead to violations and effort should be made to assure adequate computerized and human controls.

Footnotes:

The phrase ‘remotely piloted’ can pertain with respect to use of land-based, naval, and air and space robotics. Eg remotely controlled robots are used during war and domestic law enforcement to find and dismantle explosives and some can sniff for chemical or bacteriological/biological weaponry. Some fully autonomous vehicles, mines, and other mechanisms are not ‘piloted’, but are addressed. One publication notes that ‘Autonomous systems are also part of the projected ground forces’ and that there will be ‘a reconfigurable skirmishing vehicle’, a ‘stealth tank’, ‘unmanned supply lorries and mine-clearing vehicles’, ‘a small, tracked robot vehicle that can undertake missions normally done by a single soldier’, and ‘aerial robots dropping ground robots and using a few special forces to guide them’, ‘Autonomous Vehicles: Robot Wars’ (6 Jun 2011) Engineer 20. Concerning various types of military robotics, see Patrick Lin, George Bekey, and Keith Abney, ‘Autonomous Military Robotics: Risk, Ethics, and Design’ (20 Dec 2008), 1, 5–6, 11–19, available at <http://ethics.calpoly.edu/ONR_report.pdf>. Today, most attention is paid to use of aerial vehicles or drones that are remotely piloted, and these are the vehicles that are primarily addressed in this chapter.

There is a difference between use of force and war or ‘warfare’. Eg it is widely understood that the use of armed force against certain non-state actors in self-defence can be permissible under the UN Charter but not create an international or non-international armed conflict, however long or short. See also nn 51 and 55. Although war has never been merely state to state, whether a state is at war and it is international in character depends upon the status of opponents (eg whether they are states, nations, peoples, belligerents, or insurgents). This is one reason why the self-defence paradigm is different than the law of war paradigm.

UN Charter, Preamble.

UN Charter, Art 2(4).

UN Charter, Art 42; see also Art 53 (‘enforcement action’).

UN Charter, Art 52. Concerning permissible ‘regional action’ taken by NATO and the Organization of American States (OAS), see eg Christine Gray, International Law and the Use of Force (Oxford: Oxford University Press, 2000), 113 (the Cuban Missile Crisis was authorized as ‘regional peacekeeping under Chapter VIII of the UN Charter’. But see at 40 (NATO authorization regarding Kosovo without Security Council authorization was supposedly of ‘doubtful’ validity)); Jordan J. Paust, ‘Use of Armed Force Against Terrorists in Afghanistan, Iraq, and Beyond’ (2002) 35 Cornell International Law Journal 533, 545–7; Abram Chayes, ‘The Legal Case for U.S. Action in Cuba’ (1962) 47 Department of State Bulletin 763, 764 (OAS General Assembly resolution authorized forceful interdiction of Soviet vessels heading to Cuba); cf Yoram Dinstein, War, Aggression and Self-Defence (4th edn, Cambridge: Cambridge University Press, 2005), 310–14 (missing the point that Art 52 provides for ‘regional action’ when the Security Council is unable to act and to authorize ‘enforcement action’ as such).

UN Charter, Art 51.

With respect to permissible self-determination assistance, see eg Paust, ‘Use of Armed Force Against Terrorists’, 547–8; Jordan J. Paust, ‘International Law, Dignity, Democracy, and the Arab Spring’ (2012) Cornell International Law Journal 46.

See eg Eyal Benvenisti, ‘The Legal Battle to Define the Law on Transnational Asymmetric Warfare’ (2010) 20 Duke Journal of Comparative and International Law 339, 353 fn 40 (computer programs can provide estimates of consequences of drone targeting); Laurie R. Blank, ‘After Top Gun: How Drone Strikes Impact the Law of War’ (2012) 33 University of Pennsylvania Journal of International Law 675, 687–9, 691–4, 697–8, 701–2; Aaron M. Drake, ‘Current U.S. Air Force Drone Operations and Their Conduct in Compliance with International Humanitarian Law—An Overview’ (2011) 39 Denver Journal of International Law and Policy 629, 637–40, 642–5; Michael W. Lewis, ‘Drones and the Boundaries of the Battlefield’ (2012) 47 Texas International Law Journal 293, 297–8; Jordan J. Paust, ‘Self-Defense Targetings of Non-State Actors and Permissibility of U.S. Use of Drones in Pakistan’ (2010) Journal of Transnational Law and Policy 237, 274, available at <http://ssrn.com/abstract=1520717>; Jordan J. Paust, ‘Permissible Self-Defense Targeting and the Death of bin Laden’ (2011) 39 Denver Journal of International Law and Policy 569, 572–3 and fn 20; Michael N. Schmitt, ‘Drone Attacks Under the Jus ad Bellum and Jus in Bello: Clearing the “Fog of Law”’ (2010) 13 Yearbook of International Humanitarian Law 311, 313–14, 320; see also Anna Stolley Persky, ‘Lethal Force’ (Mar 2012) Washington Lawyer 23, 29 (some claim that computers can use face recognition in connection with specific targetings but worry about automated targeting without human direction).

10  See eg Case Concerning Oil Platforms (Iran v. US), 6 Nov 2003, ICJ Rep 2003, 161, 183, para 43; Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion of 8 July 1996, ICJ Rep 1996, 226, 245, para 41 (‘submission of the exercise of the right of self-defense to the conditions of necessity and proportionality is a rule of customary international law’), 246, para 46 (‘belligerent reprisals…would, like self-defense, be governed inter alia by the principle of proportionality’); Case Concerning Military and Paramilitary Activities in and against Nicaragua (Nicaragua v. US), 27 June 1986, ICJ Rep 1986, 14, 94, para 176 (UN Charter, Art 51 does not mention that ‘self-defense would warrant only measures which are proportional to the armed attack and necessary to respond to it, a rule well established in customary international law’, but this demonstrates the interface that exists between treaty provisions and customary precepts), 103, para 194; Thomas M. Franck, ‘On Proportionality of Countermeasures in International Law’ (2008) 102 American Journal of International Law 715, 719–21 (noting the ICJ’s ability to use the general principle of proportionality first, to determine whether there is a right to use force in self-defence (jus ad bellum) and, secondly, ‘whether the level of countermeasures deployed is permitted by law; whether it is proportionate to the attack itself and to the needs of self-defense (jus in bello)’); Paust, ‘Self-Defense Targetings of Non-State Actors’, 269–76. See also Judith Gardam, Necessity, Proportionality and the Use of Force by States (Cambridge: Cambridge University Press, 2004), 30, 141–8.

Since the general principles are the same, it is rational and policy-serving to consider guidance with respect to their meaning and application that is offered in relevant trends in decisions under both the jus ad bellum and jus in bello, especially regarding measures of self-defence outside the context of war when the laws of war do not apply but offer more detailed interpretive and decisional guidance. See eg Paust, ‘Self-Defense Targetings of Non-State Actors’, 269–70, 274, 279. For some, this might involve a change from rigid boxed-in thinking as if developments in one box have had no influence and are of no interpretive value within the other box. More generally, ‘legal subsystems in isolation from the remaining bulk of international law are inconceivable. There will always be some degree of interaction, at least at the level of interpretation.’ Bruno Simma and Dirk Pulkowski, ‘Of Planets and the Universe: Self-Contained Regimes in International Law’ (2006) 17 European Journal of International Law 483, 492.

11  cf Oil Platforms, 195, para 72 (‘the mining of a single military vessel might be sufficient to bring into play the “inherent right of self-defense”’); see n 48.

12  Concerning use of the phrase ‘remotely piloted aircraft’ (RPA) and other acronyms, see eg Drake, ‘Current U.S. Air Force Drone Operations and Their Conduct in Compliance with International Humanitarian Law’, 630 and fn 2; Chris Jenks, ‘Law From Above: Unmanned Aerial Systems, Use of Force, and the Law of Armed Conflict’ (2009) 85 North Dakota Law Review 649, 653 (using the acronym UAS, for Unmanned Aerial Systems).

13  See Drake, ‘Current U.S. Air Force Drone Operations and Their Conduct in Compliance with International Humanitarian Law’, 630 (the US has used drones during the last 50 years for reconnaissance and to safely observe the battlefield), 638–9 (outlining some uses of RPA for intelligence-gathering during war); Jenks, ‘Law From Above: Unmanned Aerial Systems, Use of Force, and the Law of Armed Conflict’, 654 and fn 22 (Hezbollah used drones along the Israel–Lebanon border during war in 2006).

14  eg some police departments are keen on acquiring drones for surveillance, investigation, and other law enforcement purposes. Drones will also be used for public and private security and investigation, espionage, news gathering, automobile traffic information, weather monitoring, private witnessing of events, crop dusting, and other purposes. See also ‘Video and Human Rights: Visibility Before All’, The Economist, 14 Jan 2012, 48 (‘Organizers of Occupy protests in America have used’ drone helicopters ‘to spot weaknesses in police lines’ and to take aerial pictures); ‘Drones Set to Play an Important Role Fighting Terrorism’, China Daily, 20 May 2011 (online) (China is likely to use more drones for security purposes, including reconnaissance along border areas and in municipalities ‘for use in emergencies, for the monitoring of traffic and the pursuit of suspects’); Scanning the Future of Law Enforcement’ (2010) 44 Futurist 22 (‘unmanned robots and drones…could be used by gangs and other criminal elements to attack their prey or one another. Low-cost airships or small submarines could be used to transport narcotics and other contraband…[and] hinder efforts to assign responsibility’); Editorial, ‘Big Brother’, National Post, 7 Oct 2008, A16 (‘British police…employ cameras mounted on remote-controlled mini-drones to fly above crowds and look for suspicious activity’); Damian Inwood, ‘Massive Security Planned for Games’, Vancouver Province, 21 May 2008, A3 (use of drones and cameras with face-recognition capabilities during Canadian Olympic Games).

15  eg drones have been used along the US border with Mexico for surveillance with respect to smuggling and other unlawful activities.

16  NGOs can use drones to verify, monitor, and document human rights violations and international crimes. See eg Andrew Stobo Sniderman and Mark Hanis, ‘Drones for Human Rights’, New York Times, 31 Jan 2012, A25 (‘Drones are increasingly small, affordable and available to nonmilitary buyers…An environmental group, the Sea Shepherd Conservation Society, has reported that it is using drones to monitor illegal Japanese whaling’). One can predict that state, regional, and UN forces will do the same.

17  See eg Tim Lister, ‘Crashed Drone Was Looking at Iran Nuclear Sites’, CNN, 15 Dec 2011, available at <http://security.blogs.cnn.com/2011/12/15/crashed-drone-was-looking-at-iran-nuclear-sites>; Rick Gladstone, ‘Stop U.S. Drone Flights, Iran Warns Afghanistan’, New York Times, 16 Dec 2011, A11; ‘US, Iran Take War to Cyber Space’, Hindustan Times, 15 Dec 2011 (online); Saeed Kamali Dehghan, ‘Iran Announces Exhibition of US Spy Drone—and Six Others’, The Guardian, 16 Dec 2011, 33.

18  Steve Lohr, ‘Smarter Than You Think; Computers That See You, Read You and Even Tell You to Wash’, New York Times, 2 Jan 2011, A1.

19  See eg Blank, ‘After Top Gun’, 678; Jenks, ‘‘Law From Above’, 653; Lin, Bekey, and Abney, ‘Autonomous Military Robotics’, 11–19; Gary E. Marchant et al, ‘International Governance of Autonomous Military Robots’ (2011) 12 Columbia Science and Technology Law Review 272, 276–8.

20  See eg Drake, ‘Current U.S. Air Force Drone Operations and Their Conduct in Compliance with International Humanitarian Law’, 652 (some weapons that are already in use are ‘capable of operating, essentially in fully autonomous modes’, such as the US Navy’s Phalanx Close-In Weapons System (CIWS) that ‘automatically performs “search, detect, evaluation, track, engage and kill assessment functions”’, and the US Army’s Counter Rocket, Artillery, and Mortar system (C-RAM) that is employed on land and that must be used in a manner that does not result in indiscriminate death, injury, or suffering); Michael W. Lewis, ‘Response, Law and Ethics for Robot Soldiers’, Opinio Juris Blog, 2 May 2012 (‘CIWS on naval vessels are already examples of automated defensive weapons systems designed to hit incoming missiles, although the decision to turn the CIWS to automatic mode is still made by a human being’), available at <http://opiniojuris.org/2012/05/01/law-and-ethics-for-robot-soldiers>; Lin, Bekey and Abney, ‘Autonomous Military Robotics’, 7, 11–19; Marchant et al, ‘International Governance of Autonomous Military Robots’, 276–8, 286–7 (addressing types of lethal autonomous robots (LARS)).

21  See eg Lewis, ‘Drones and the Boundaries of the Battlefield’, 295 (‘there is nothing legally unique about using unmanned drones as a weapons delivery platform that requires the creation of new or different laws’), 297–8; Michael A. Newton, ‘Flying into the Future: Drone Warfare and the Changing Face of Humanitarian Law’ (2011) 39 Denver Journal of International Law and Policy 601, 605–6; Mary Ellen O’Connell, ‘The Resort to Drones Under International Law’ (2011) 39 Denver Journal of International Law and Policy 585, 599 (current law is adequate); Schmitt, ‘Drone Attacks Under the Jus ad Bellum and Jus in Bello’; Markus Wagner, ‘Taking Humans Out of the Loop: Implications for International Humanitarian Law’ (2011) 21 Journal of Law, Science and Technology (but stating that fully autonomous weapons are unable to make qualitative assessments and are presently ‘legally indefensible’); Kenneth Anderson, ‘Law and Ethics for Robot Soldiers’, Opinio Juris Blog, 1 May 2012 (urging ‘a gradually evolving pattern of practices of the states developing the systems…through increased reasoned articulation of how and why highly particular technically detailed weapons systems meet fundamental legal standards’); cf Marchant et al, ‘International Governance of Autonomous Military Robots’, 298 (some call for a new treaty to limit use of lethal autonomous robots).

22  See generally Blank, ‘After Top Gun’, 679; Laurie R. Blank and Benjamin R. Farley, ‘Characterizing US Operations in Pakistan: Is the United States Engaged in an Armed Conflict?’ (2011) 34 Fordham International Law Journal 151, 152–3; Paust, ‘Permissible Self-Defense Targeting and the Death of bin Laden’, 572–3; Schmitt, ‘Drone Attacks Under the Jus ad Bellum and Jus in Bello’.

23  See eg Afsheen John Radsan and Richard Murphy, ‘The Evolution of Law and Policy for CIA Targeted Killing’ (2012) 5 Journal of National Security Law and Policy 439, 441 (‘The lower “costs” of drone strikes…encourage governments to resort to deadly force more quickly—a trend that may accelerate as drone technology rapidly improves and perhaps becomes fully automated through advances in artificial intelligence’, and paradoxically, might ‘lead to an increase in deadly mistakes’); see also Lin, Bekey, and Abney, ‘Autonomous Military Robotics’, 46, 75; Marchant et al, ‘International Governance of Autonomous Military Robots’, 285; O’Connell, ‘The Resort to Drones Under International Law’, 599 (‘We do not have a full study of the psychological impact on operators or on our leaders of this new technology—some indicators suggest it is leading to more killing’); Noel Sharkey, ‘Robot Wars as a Reality’, The Guardian, 18 Aug 2007, 29.

24  See n 9.

25  These are among appropriate considerations for choice and compliance with the principles of reasonable necessity, distinction, and proportionality. See eg Geoffrey S. Corn and Lieutenant Colonel Gary P. Corn, ‘The Law of Operational Targeting: Viewing the LOAC Through an Operational Lens’ (2012) 47 Texas International Law Journal 337, 342–3, 349–53, 362–6, 370–1, 380 (often emphasizing the need for human ‘operational art’ and adequate awareness of many contextual variables); Amos N. Guiora, ‘Determining a Legitimate Target: The Dilemma of the Decision-Maker’ (2012) 47 Texas International Law Journal 315, 322–3, 331–6; Paust, ‘Permissible Self-Defense Targeting and the Death of bin Laden’, 576; Paust, ‘Self-Defense Targetings of Non-State’, 275–7; Afsheen John Radsan and Richard Murphy, ‘Measure Twice, Shoot Once: Higher Care for CIA Targeted Killing’ (2011) University of Illinois Law Review 101 (addressing a six-step US military decisional and review process with respect to drone and related types of targeting and suggesting similar choice-making by CIA personnel); Radsan and Murphy, ‘The Evolution of Law and Policy for CIA Targeted Killing’, 459, 461–2 (also warning that choice cannot be made ‘with mathematical certainty—in part because such judgments implicate contestable facts and competing values’); see also Marchant et al, ‘International Governance of Autonomous Military Robots’, 285 (doubts exist whether autonomous robots will be capable of making appropriate choices and avoiding indiscriminate killing and wounding).

26  See eg ‘Autonomous Vehicles: Robot Wars’ (‘Everyone talks about there being a human in the loop’, quoting Noel Sharkey, a professor of artificial intelligence and robotics); Marchant et al, ‘International Governance of Autonomous Military Robots’, 275–6 (‘military systems (including weapons) now on the horizon will be too fast, too small, too numerous, and will create an environment too complex for humans to direct’, quoting Thomas K. Adams, ‘Future Warfare and the Decline of Human Decisionmaking’ (2001–2) Parameters, US Army War College Quarterly 57–5), 283–5.

27  Concerning certain past failures, see eg Lin, Bekey, Abney, ‘Autonomous Military Robotics’, 7.

28  As older generations of the legally trained might recall, use of spring-guns to guard property had famously led to criminal prosecutions for reckless and negligent homicide and to private lawsuits.

29  Recall n 20.

30  This problem has been recognized. See Lin, Bekey, and Abney, ‘Autonomous Military Robotics’, 23 (adding that the problem can occur even with aerial robotics that use stored maps and GPS guidance).

31  That aircraft and vessels are the equivalent of the territory of the flag under international law, see eg The SS Lotus, 1927 PCIJ, Ser A, No 10 (a Turkish vessel was assimilated to Turkish territory); Hirsi Jamaa and Others v. Italy (App no 27765/09), ECtHR, 23 Feb 2012 (Grand Chamber); Jordan J. Paust et al, International Criminal Law (3rd edn, Leiden: Brill, 2007), 175–6; R v. Anderson (1868) 11 Cox CC 198 (UK Court of Criminal Appeal).

32  See Section IV.A.

33  With respect to such a distinction and self-defence, see eg Jordan J. Paust, ‘A Critical Appraisal of the Air and Missile Warfare Manual’ (2012) 47 Texas International Law Journal 277, 286, and fn 50.

34  Nicaragua, 146, para 292(6).

35  See n 11.

36  ‘Autonomous Vehicles: Robot Wars’.

37  ‘Autonomous Vehicles: Robot Wars’.

38  See eg Paust et al, International Criminal Law, 696–8; Drake, ‘Current U.S. Air Force Drone Operations and Their Conduct in Compliance with International Humanitarian Law’, 652–3, 657–8.

39  See n 23.

40  UN Charter, Preamble.

41  See UN Charter, Art 24(2) (‘the Security Council shall act in accordance with the Purposes and Principles of the United Nations’), 25 (‘The Members of the United Nations agree to accept and carry out the decisions of the Security Council in accordance with the present Charter’), 52 (‘regional action’ can be taken by regional organizations, ‘provided…[that such] activities are consistent with the Purposes and Principles of the United Nations’). Such purposes and principles include, among others, the need to assure that armed force shall not be used save in the common interest and the need to serve peace, security, self-determination of peoples, and human rights. See Preamble, Arts 1, 55.

42  Concerning the express prohibition of merely three types of armed force under Art 2(4) of the Charter, see eg Paust, ‘Use of Armed Force Against Terrorists’, 536–7; see also John Norton Moore et al, National Security Law (Durham, NC: Carolina Academic Press, 1990), 131; Anthony D’Amato, ‘The Invasion of Panama Was a Lawful Response to Tyranny’ (1990) 84 American Journal of International Law 516, 520; Michael Reisman and Myres S. McDougal, ‘Humanitarian Intervention to Protect the Ibos’ in Richard B. Lillich (ed), Humanitarian Intervention and the United Nations (Charlottesville, VA: University Press of Virginia, 1973), 166, 177; Carsten Stahn, ‘Enforcement of the Collective Will After Iraq’ (2003) 97 American Journal of International Law 803, 816. But see Dinstein, War, Aggression and Self-Defence, 87–8; O’Connell, ‘The Resort to Drones Under International Law’, 589 (preferring all force above ‘de minimis’); Christian J. Tams, ‘The Use of Force Against Terrorists’ (2009) 20 European Journal of International law 359, 364–5 (also noting early and decades long disagreement), 375.

43  UN Charter, Art 2(4). To conclude that this phrase precludes all uses of armed force ignores the fact that some armed force may be ‘inconsistent with’ the purposes of the UN whereas others may, on balance, be consistent. Eg force may thwart peace in the short run but serve peace in the long term as well as regional security, self-determination of peoples, and human rights. Therefore, the phrase ‘inconsistent with’ necessarily demands awareness of context and whether UN purposes are generally being thwarted or served. See Paust, ‘Use of Armed Force Against Terrorists’, 536–7 (also noting, however, that mere ‘preemptive or retaliatory’ uses of force are widely expected to be impermissible).

44  See n 41.

45  With respect to the express need for an armed attack, see eg Dinstein, War, Aggression and Self-Defence, 183–5; Paust, ‘Use of Armed Force Against Terrorists’, 534 and fn 2. However, the equally authentic French version of Art 51 speaks about the existence of an agression armée (ie an armed aggression). See Paust, ‘Self-Defense Targetings of Non-State Actors’, 241 fn 4.

46  See n 10.

47  See Paust, ‘Self-Defense Targetings of Non-State Actors’, 238–41 and fn 3 (noting that the vast majority of text-writers recognize that armed attacks by non-state actors can trigger the inherent right of self-defence).

48  See also Nicaragua, 101, para 191 (need ‘to distinguish the most grave forms of the use of force (those constituting an armed attack) from other less grave forms’); Oil Platforms, 187, para 51 (quoting Nicaragua, para 72), 195, para 72 (quoted in n 11); Dinstein, War, Aggression and Self-Defence, 193, 195 (‘it would be fallacious to dismiss automatically from consideration as an armed attack every frontier incident’, such as when a soldier fires a single bullet across a border or a small military unit is attacked; ‘The gravity of an attack may affect the proper scope of defensive use of force…, but it is not relevant to determining whether there is a right of self-defense in the first instance’ (quoting William H. Taft, IV, former Legal Adviser to the US Secretary of State); ‘even a small border incident’ can constitute an armed attack (quoting J. L. Kunz)), 202 (cumulative ‘pin-prick’ attacks can be viewed as a process of armed attack), 230–1; Gardam, Necessity, Proportionality and the Use of Force by States, 143, 161; Tams, ‘The Use of Force Against Terrorists’, 370 and fns 69, 71 (noting that a gravity threshold articulated in 1986 ‘remained controversial’, citing Dahm, Dinstein, Feder, Gazzini, and Randelzhofer), 379–81 (noting new practice of states). I agree with Dinstein, Kunz, Taft, and others who recognize the need to abandon an unrealistic gravity limitation.

49  Paust, ‘Self-Defense Targetings of Non-State Actors’, 255–6. See also n 48.

50  Consider O’Connell, ‘The Resort to Drones Under International Law’, 589, 592–4, 599.

51  See n 47. If responsive force is directed merely against the non-state actors who are perpetrating ongoing armed attacks, the use of force against them in a foreign state in compliance with Art 51 of the UN Charter is not a use of force against the foreign state, an attack ‘on’ or ‘against’ its territory, or a use of force in violation of its territorial ‘integrity’ within the meaning of Art 2(4) and, moreover, the two states would not be at war. See eg Paust, ‘Self-Defense Targetings of Non-State Actors’, 256, 258–9, 279. Importantly, there are no geographic limits with respect to armed attacks that trigger the inherent right of self-defence. Eg an armed attack by a group that initiates a war between a nation or people and a state, a belligerency, or an insurgency within a single state can justify use of responsive armed force in self-defence. See also Paust, ‘Use of Armed Force Against Terrorists’, 534 (‘nothing in the language of Article 51 requires that such an armed attack be carried out by another state, nation, or belligerent, as opposed to armed attacks by various other non-state actors’); Jordan J. Paust and Albert P. Blaustein, ‘War Crimes Jurisdiction and Due Process: The Bangladesh Experience’ (1978) 11 Vanderbilt Journal of Transnational Law 1, 11 fn 39 (where an armed attack occurs by a government against a people undergoing a process of self-determination, such people should have the right of self-defense and the right to seek self-determination assistance in accordance with the principles and purposes of the UN Charter).

52  See eg Dinstein, War, Aggression and Self-Defence, 184–5, 204–8; Paust, ‘Self-Defense Targetings of Non-State Actors’, 241 and fn 5. Importantly also, international law has never been merely state to state. See eg Jordan J. Paust, ‘Nonstate Actor Participation in International Law and the Pretense of Exclusion’ (2011) 51 Vanderbilt Journal of International Law 977; Paust, ‘A Critical Appraisal of the Air and Missile Warfare Manual’, 279–81.

53  See Paust, ‘Self-Defense Targetings of Non-State Actors’, 241–9, 251–2; Paust, ‘Permissible Self-Defense Targeting and the Death of bin Laden’, 569–70; Michael N. Schmitt, ‘Responding to Transnational Terrorism Under the Jus ad Bellum: A Normative Framework’ in Michael N. Schmitt and Jelena Pejic (eds), International Law and Armed Conflict: Exploring the Faultlines: Essays in Honour of Yoram Dinstein (Leiden: Martinus Nijhoff, 2007), 167–8, 176–7. General consent by all members of the UN exists in advance in Art 51 of the Charter for permissible measures of self-defence and no special ad hoc consent is required.

54  See Dinstein, War, Aggression and Self-Defence, 206; Paust, ‘Permissible Self-Defense Targeting and the Death of bin Laden’, 570.

55  Paust, ‘Self-Defense Targetings of Non-State Actors’, 249–58, 279–80; and see n 51.

56  Paust, ‘Permissible Self-Defense Targeting and the Death of bin Laden’, 580–1. Nonetheless, the fact that a non-state actor attack has occurred across a border might be sufficient to demonstrate that the state was unable to control its territory.

57  Paust, ‘Permissible Self-Defense Targeting and the Death of bin Laden’, 570–1; Paust, ‘Self-Defense Targetings of Non-State Actors’, 256–7 and fns 47–8. Art 51 of the Charter is itself an agreed upon diminution of sovereignty.

58  See Paust, ‘Self-Defense Targetings of Non-State Actors’, 260–9, 271–3, 275, 279–80.