The Drone Threat, the Laser Response, and the Law – Part I
In conflicts during the last few years, unmanned air weapons, commonly referred to as drones, have increasingly been used to undertake attacks of ground targets. These attacks have recently involved large numbers of these drones, often directed at multiple targets. The targets to which these drones have been directed have reportedly not been limited to military objectives. For example, reports here, here, and here suggest that attacks by Russia have been directed at elements of critical Ukrainian civilian infrastructure. Ukraine has also reportedly been using long-range drones to attack ground targets well inside Russia. On October 7, 2023, Hamas reportedly used drones in the early stages of the events that reignited the armed conflict between Israel and Hamas, and Hezbollah has also used similar technology in the course of its armed conflict with Israel.
Before considering the technologies that are involved and the applicable law, a point should at this stage be made about terminology. The word “drone” is a colloquialism which has traditionally referred to remotely piloted aircraft. As the latter, more informative, term implies, they have in the past referred to air vehicles which, though not carrying a pilot, are controlled remotely by a human operator usually from a ground station. The unmanned aircraft, when employed to fire a weapon against ground targets, is so designed that after the operation it will return to base so that it can be re-armed and used again for a further mission.
Many of the drones that have been used in recent conflicts and that are discussed in this post are, by contrast, so designed that the entire drone, including the explosive warhead fitted to it, impacts with and explodes on the target. They are essentially deployed on a one-way operation which is, perhaps, why they are sometimes referred to as suicide or kamikaze drones. In military doctrinal terms, a weapon which is designed to navigate to a target and then explode on impact on or near that target is a cruise missile. The legal considerations that apply to more traditional cruise missiles, such as the Tomahawk Land Attack Missile, will also apply to kamikaze or suicide drones. It is the capacity of the Shahed 136 (a modern swarming drone developed and used by Iran) and other similar weapons discussed below to loiter for significant periods before undertaking the attack that potentially differentiates them from cruise missiles. While that may be a significant point of distinction in doctrinal terms, there is no difference in the requirements of international law that apply to these types of weapons.
What Are the Weapons Law Rules?
The use of these kamikaze or suicide drones to attack ground targets does not, per se, breach international law. Indeed, there is no specific rule of international law prohibiting or restricting the use of such weapons. The weapon systems must, however, comply with the general principles and rules of weapons law. In this context, Article 22 of the Hague Regulations 1907 stipulates that the right of parties to an armed conflict to adopt means of injuring the enemy is not unlimited.
The first substantive principle of weapons law, the superfluous injury/unnecessary suffering principle, prohibits weapons that are of a nature to cause injury or suffering for which there is no corresponding military purpose. This is a rule that protects combatants (and directly participating civilians) from weapons that in the intended circumstances and manner of use needlessly aggravate a wound or inflict gratuitous injury or suffering. It suffices to note that the employment in warfare of warheads that combine blast and fragmentation as the damaging and injuring mechanism does not, per se, raise legal issues under this principle.
The second principle of weapons law, as reflected in Additional Protocol I, Article 51(4)(b) and (c), prohibits weapons that are indiscriminate by nature. The issue under this principle will be whether the weapon can be directed at a military objective and whether its effects can be reasonably limited to the military objective. Weapons that target military objectives, civilians, and civilian objects without distinction are prohibited. If the kamikaze or suicide drone were to be remotely controlled by a human operator, that operator would be responsible for ensuring that the weapon is indeed directed at a lawful target. If the missile is operating without a human being either controlling it or, at least, monitoring its actions and able to intervene if necessary, the issue will then be whether the technology enables the weapon to be aimed at a military objective. The technology associated with the particular drone or missile will, however, be of critical importance in determining whether the weapon can in fact be directed to a target.
The third rule that is generally applied when determining the lawfulness of a weapon system concerns the environmental impact of the weapon. This rule is more relevant to the characteristics and content of the warhead rather than the unmanned nature of the delivery system and will, therefore, not be considered further in this post, save to say that rules relating to the environment are only likely to be breached by a level of environmental damage well above that likely to be caused by conventional blast/fragmentation warheads.
The final matter that needs to be considered with some new weapon technologies such as highly automated and autonomous weapon systems is whether the principles and rules of the law of targeting are capable of being applied. That matter can only be addressed by reference to the particular weapon and the specific technology it employs. The possibility of applying targeting law is a weapons law issue as it is concerned with the general way in which the weapon system operates; this should be contrasted with the targeting law issue of whether a particular attack on a particular occasion against a particular target is lawful. So, whether targeting law can be applied when a weapon system is used must be contrasted with the fundamentally different targeting law question, discussed later in this post, of whether specific attacks comply with the applicable law.
Applying Weapons Law to Specific Drone Systems
Authoritative reports here and here describe the Iranian Shahed 136 “suicide drone” that has been supplied to Russia for use against Ukraine and that has been named by Russia the Geran 2. Similar weapons are now increasingly produced in Russia. The Shahed 136 weapon has a delta wing, is 3.5 metres long with a wingspan of 2.5 metres. Its propulsion comes from a 50 HP two-stroke, 4-piston engine, and it weighs approximately 200 kg. Its navigation comprises commercial inertial navigation, GPS, and satellite navigation. “It also carries a commercial grade digital communication device that allows it to receive updates on its target’s location or even change targets. Its warhead is variously estimated to carry 20 to 40kg of explosives.” A high percentage of the weapon’s components are reportedly of western origin. Unit cost is estimated at between U.S. $20,000 and U.S. $30,000.
Other States and organised armed groups also possess and employ suicide or kamikaze drones. For example, in August 2023, Ukraine commenced production of the Rubaka drone which reportedly has a range of up to approximately 500 km, uses inertial navigation system technology to attack pre-set co-ordinates, and costs approximately U.S. $15,000 per unit. It is also clear that the Houthis have developed a large arsenal of drones, including suicide or kamikaze drones, for use in Yemen and elsewhere and have applied related surface technologies for use against shipping. Hezbollah is also, for example, said to have used a kamikaze drone to attack an Israel Defence Forces training base near Binyamina, south of Haifa on October 13, 2024.
It would seem to be clear from the basic description of the Shahed 136, in particular from the navigation systems with which it is equipped, from its connectivity, and from its reported battlefield performance, that the weapon is certainly capable of being directed at a military objective and that it cannot therefore be described as indiscriminate by nature. This is because, as with any cruise missile, if the weapon can be fired towards an identified target with a reasonable level of assurance that it will hit the intended target in a discriminating way, it will not be indiscriminate by nature.
Some discussions of recent drone attacks describe the numerous drones involved as constituting swarms. There is, in the author’s view, no legal significance in that characterisation as, indeed, there is no legal significance in the use of the term “drone.” The word “swarm” is, it seems, merely being used to indicate that large numbers of these weapons are fired at the same time in an evident attempt to overwhelm defensive measures.
In the author’s view, there is no international law principle or rule that prohibits the use of overwhelming force during an armed conflict provided that the principles and rules of weapons law and targeting law, as briefly summarised in this post, are complied with. If, therefore, the effect of using a swarm method of attack is that the individual weapons attack military objectives and civilians and civilian objects without distinguishing between them, this would render the swarm attack indiscriminate and, thus, unlawful.
What Are the Targeting Law Rules?
The basic rule of targeting law, set forth in Article 48 of Additional Protocol I but binding on all States as an accepted customary principle of law, stipulates as follows,
In order to ensure respect for and protection of the civilian population and civilian objects, the Parties to the conflict shall at all times distinguish between the civilian population and combatants and between civilian objects and military objectives and accordingly shall direct their operations only against military objectives.
In so far as objects are concerned, military objectives are limited by Article 52(2) of Additional Protocol I to “those objects which by their nature, location, purpose or use make an effective contribution to military action and whose total or partial destruction, capture or neutralisation, in the circumstances ruling at the time, offers a definite military advantage.” All objects which do not come within this definition are civilian objects and must not therefore be made the object of attack.
Indiscriminate attacks are prohibited by Article 51(4) of the same treaty. They would include, but would not be limited to, attacks that “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.” (Additional Protocol I, art. 51(5)(b)). The final targeting law rule that must be mentioned is Article 54(2), which states, “It is prohibited to attack, destroy, remove or render useless objects indispensable to the survival of the civilian population … for the specific purpose of denying them for their sustenance value to the civilian population or to the adverse Party, whatever the motive … .”
Much more could indeed be said about the relevant rules of targeting law, and the author has indeed done so in the past. For the purposes of the present discussion, the cited principle and rules suffice to show that the deliberate targeting of civilian objects, particularly objects that are essential to the survival of the civilian population, is unlawful.
However, the mere fact that in media reporting a facility is described as being part of civilian infrastructure does not automatically mean that the facility is a civilian object. So, for example, the cables and electricity substations that supply power to a military installation such as a military barracks, a military port, a military airfield, military radar facilities, or military command and communications equipment are going to satisfy the military objective definition because they are supplying the power that enables those military systems to perform their function. Yoram Dinstein points out that the Eritrea-Ethiopia Claims Commission determined that “electric power stations serving the military or the war industry are military objectives whereas segregated generators supporting medical facilities or other civilian uses are not.” Professor Dinstein goes on to note that when the national grid is integrated, distributing electricity for both the armed forces and the civilian population, “we are faced with a ‘dual-use’ target.”
Studies, for example here, show that electricity generation and distribution facilities have been targeted during armed conflicts since 1939, including the Second World War, Korea, Vietnam, and Operation Desert Storm. As recognised by the Oslo Manual, Rule 84, “[t]he status of a military objective by ‘nature’ is not altered, even if it is also used for civilian purposes.” The point here is that so-called dual-use objects are military objectives on the basis that, by virtue of their military use, they make an effective contribution to military action such that their destruction offers a definite military advantage.
The mere characterisation of an object as a military objective does not necessarily justify an attack against it. This is where the prohibition of indiscriminate attacks and of attacks that may be expected to breach the proportionality rule comes in, remembering that the latter is merely an example of the former. In applying the proportionality rule, a careful assessment of the anticipated military advantage and of the expected death or injury to civilians and damage to civilian objects is required. Where anticipated military advantage is concerned, the issue will be to what extent will the attacks, and the consequent power interruptions, actually have an adverse effect on enemy military action. If, as is highly likely, enemy military facilities, particularly those with key war-fighting roles, have back-up generators, the military advantage to be anticipated from such attacks may be rather limited, whereas the impact of electricity denial on civilians in times when the temperature falls to minus 10 degrees or lower is likely to be severe. It follows from this that several questions must be considered before an electricity grid attack can lawfully be undertaken, namely:
1. Is the electricity grid being used to make an effective contribution to military action? If no, it is not a military objective and must not be attacked. If yes,
2. What is the nature and degree of the military advantage that the planned attack, if successful, can be anticipated to yield?
3. What is the amount of collateral damage, that is death or injury to civilians and damage to civilian objects, that the attack may be expected to cause?
4. Is 3 excessive in relation to 2? If so, the attack should not be undertaken. If not,
5. Is the attack otherwise indiscriminate? If so, again the attack should not be undertaken.
Some commentators, for example here, suggest that the purpose of Russia’s drone attacks against Ukraine’s power infrastructure is “to make the Ukrainians miserable enough to give up. The Russians are trying to systematically break apart Ukraine’s power grid because it could face a rough winter.” It should be emphasised that effects-based attacks of this nature are not prohibited provided that the target is a military objective and provided that targeting law is complied with. In this regard, the Article 54(2) prohibition referred to earlier should be considered.
In addition, it should be recalled that Article 57 of Additional Protocol I requires that constant care be taken to spare the civilian population and civilian objects, and specifically that “all feasible precautions [must be taken] in the choice of means and methods of attack with a view to avoiding, and in any event to minimizing, incidental loss of civilian life, injury to civilians and damage to civilian objects.” Further key questions with regard to these drone attacks against the electricity grid arise as follows:
6. Is the object of the attacks, namely the power grid, indispensable to the survival of the civilian population? And, if so,
7. Are the attacks undertaken for the specific purpose of denying power for its sustenance value to the civilian population for example to deny the population the electrical power to provide heat and warmth during the cold, dark winter months? If both 6 and 7 apply, the attack should not be undertaken.
8. Irrespective of 6 and 7 above, are all feasible precautions being taken to avoid and/or minimize incidental loss of civilian life, injury to civilians and damage to civilian objects?
The author is content to identify those key questions. A more detailed discussion of the precautionary rules listed in Article 57 of Additional Protocol I and of the international crimes associated with breaches of the core principle and rules discussed in this section lies outside the scope of this post. The focus of the discussion should now turn to the ways in which the drone threat discussed in the preceding sections might be countered using laser technology, and that is the subject of Part II of this post.
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Air Commodore William H. Boothby retired as Deputy Director of Royal Air Force Legal Services in July 2011. He is Honorary Professor at the Australian National University and also teaches at the University of Southern Denmark and at the Geneva Centre for Security Policy.
Photo credit: Tasnim News Agency
