The deliberations of the Group of Governmental Experts (GGE) on Emerging Technologies in the Area of Lethal Autonomous Weapon Systems (LAWS) underscore the critical importance of legally defining or characterising the term “lethal” in the context of autonomous weapon systems (AWS). The Report of the Secretary General on LAWS stated that some “States considered the word ‘lethal’ to be an important reference to a system’s capability to apply lethal force. Others were of the view that the lethality of a weapons system depended on its use rather than on its design. Several States argued against the use of the word ‘lethal’, stating that it had no basis in international humanitarian law and noting, inter alia, that lethality was an effect of the manner in which a weapon was used.” In the context of LAWS, understanding lethality has significant implications for the scope of the prohibition or restriction of such weapons and the applicability of international humanitarian law (IHL) and the 1980 Convention on Certain Conventional Weapons (CCW). This post explores the legal basis of the term “lethal” by examining its application across various legal contexts.
A weapon is generally understood as that aspect of the system used to cause damage or destruction to objects or injury or death to persons. Although terms like ‘lethal,’ ‘non-lethal,’ and ‘less-lethal’ are used by states and international organisations to indicate the destructive capacity of a weapon, there is no legal definition for these terms and their meaning remains ambiguous. For instance, the CCW and its protocols impose prohibitions or restrictions on specific types of weapons, such as blinding laser weapons, incendiary weapons, and anti-personnel mines, due to their inherently indiscriminate effects or the potential to cause excessive injury. While the Framework Convention and its protocols frequently reference terms like “kill” and “injury,” they notably do not include the term “lethal,” which lacks a precise characterization and legal definition in IHL or multilateral treaties concerning the disarmament of weapons of mass destruction (WMDs), such as nuclear, chemical, and biological weapons.
The classification of weapons as ‘lethal,’ ‘non-lethal,’ and ‘less-lethal’, based on design and intended use, may have implications for the prohibition or restriction of their use. For example, an instance of intention to omit certain category of weapons from the scope of an international instrument is evident in the context of the Amended Protocol II to the Convention on CCW. The declaration by Israel and the reservation by the United States state that “nothing in Amended Protocol II may be construed as restricting or affecting in any way non-lethal weapon technology that is designed to temporarily disable, stun, signal the presence of a person, or operate in any other fashion, but not to cause permanent incapacity.” Similarly, NATO defines non-lethal weapons as “weapons which are explicitly designed and developed to incapacitate or repel personnel, with a low probability of fatality or permanent injury, or to disable equipment, with minimal undesired damage or impact on the environment.” Thus, a key characteristic of non-lethal weapons is the use of non-lethal force aimed at incapacitation rather than elimination. However, it may be noted that the non-lethal use of force could also lead to violations of IHL. For example, some non-lethal weapons, such as blinding laser weapons, have already been assessed by the international community as causing unnecessary suffering.
The term “less-lethal” is mostly associated with use of weapons in law enforcement, however, scholarly articles cite the use of less-lethal weapons in armed conflict, including scenarios of occupation. The UN Guidance on Less-Lethal Weapons in Law Enforcement defines it as follows: “weapons designed or intended for use on individuals or groups of individuals and which, in the course of expected or reasonably foreseen use, have a lower risk of causing death or serious injury than firearms. Less-lethal ammunition may be fired from conventional firearms. For the purpose of this Guidance, the term includes conventional firearms when they are used to discharge less-lethal ammunition, but not when they are used to discharge conventional bullets or other ammunition that would be likely to result in life-threatening injuries.” The ICRC cautioned that “the risks associated with the use of less-lethal weapons, including the risks of serious injury or death, and the risks of excessive force if the use of such weapons is not carefully controlled.” However, since less-lethal weapons are generally not designed to cause superfluous injury or indiscriminate effects, they are – despite the broad terminology used in most arms control treaties – in principle not covered by the CCW or its Protocols.
When it comes to the term ‘lethal’, it is so far understood in terms of the degree and certainty of harm a weapon may inflict. For instance, both conventional weapons and nuclear weapons produce lethal effects, but with varying deleterious effects. The World Health Organization’s 1987 study clearly describes the gravity of the destructive force of nuclear weapons in comparison to conventional weapons: “in conventional weapons the two most lethal are blast and heat. Blast and heat both cause injury and death when nuclear weapons are used, but to an extent thousands of times greater. Nuclear weapons, however, also produce additional lethal effects by radiation.” Thus, although both weapons produce lethal effects, the differing intensity in the use of lethal force may have led to the distinction between conventional weapons and WMDs, with several multilateral treaties existing to outlaw various classes of WMDs.
When considering the degree of lethal force employed and the physical effects that result, a clear distinction exists between non-lethal and lethal weapons. In context of legal distinction, it has been understood that under current international law, there is no valid reason to distinguish between lethal and non-lethal weapons, as international legal principles apply to all weapons. However, this perspective has shifted with the introduction and deliberation of the term “lethal” in the GGE. This may have legal implications, potentially leading to a broad categorization of (autonomous weapons systems) AWS into lethal and non-lethal, with each of the category potentially governed by different legal regimes. The Secretary-General’s, 2023 New Agenda for Peace, indicates this distinction as “Lethal AWS” and “all other types of AWS.” It recommended States conclude a legally binding instrument by 2026 to prohibit LAWS that function without human control or oversight, and which cannot be used in compliance with international humanitarian law, and to regulate all other types of autonomous weapons systems. Thus defining the term “lethal” is critical in the identification of AWS that fall within the prohibitions and restrictions of the CCW.
At present, the rolling text, as of 28 August 2024, on working characterization of LAWS understands “lethal” as follows: “the term “lethal” in lethal autonomous weapon system is understood to encompass any such system capable of applying lethal force to targets, including in scenarios where the effects of its use in attack involve killing or injuring persons, or damaging, destroying or otherwise neutralizing or disrupting the functioning of objects.” Although the description is without prejudice to any future understanding and the potential modification of characterization of LAWS, it is necessary to clarify the following aspects in defining the term “lethal” in the context of LAWS.
First, it should be specified whether the term “lethal” applies to both the primary and secondary effects of the force that leads to the consequences mentioned in the characterization above. This distinction is apparent in the Framework Convention on the use of CCW and its protocols. For instance, Article 1 of Protocol IV states: “the prohibition on laser weapons designed with the combat function to cause permanent blindness…” Furthermore, Article 3 clarifies that “blinding as an incidental or collateral effect of the legitimate military employment of a laser weapon” is not prohibited. Second, since the purpose of the Convention is to prevent indiscriminate effects and superfluous injury prohibited by IHL, the interpretation of “lethal” should align with the Convention’s purpose by ensuring a clear identification and prevention of indiscriminate effects or superfluous injury. Third, a broad definition of “lethal,” including terms like “injury,” could create interpretational ambiguity and result in the mischaracterization of AWS designed for non-lethal use as lethal, thereby expanding the scope of restrictions or prohibitions. As Janet Morris of the U.S. Global Security Council suggested, the writers of the CCW surely never had any intention of prohibiting the development of environmentally friendly and humane non-lethals under CCW. Thus an approach, in line with notions such as responsible AI, may ensure that the development and integration of emerging technologies in AWS with the potential to enhance compliance with IHL are not prematurely labeled as “lethal” and are not unnecessarily subjected to blanket prohibitions or restrictions. Fourth, it should be clarified whether the phrase ‘neutralizing or disrupting the functioning of objects’ encapsulate “incapacitation” a key feature of non-lethal use of force. Fifth, the understanding of the term lethal must also take into account practical difficulties in applying a distinction between lethal and non-lethal weapons. Lethal weapons may have non-lethal effects and vice versa. As a 1972 report on non-lethal weapons by the US National Science Foundation explains: “all weapons […] create some primary or secondary risk of death or permanent injury. The probable seriousness of their effects (their lethality) depends on a number of factors, not all of which are determined by their design. Weapons not intended to kill or create permanent injury, if used with a degree of regularity, would undoubtedly cause some deaths because of the physiological differences among those against whom they employed, physical malfunctioning, improper utilization, and other circumstances.” Sixth, the ‘lethality’ of a weapon may also depend on its intended use. Simply put, the same knife used in the kitchen can become lethal the moment it is intended to harm a target (dual use). Similarly, emerging technologies like AI, which possess dual-use capabilities, are significantly influenced by the intent behind their use. When integrated into AWS, the same technology can either exacerbate or mitigate the lethality of such systems. Therefore, the key question is whether ‘lethal’ can be defined independently of the intention behind its use.
Although challenges exist in defining “lethal” in the context of LAWS, the GGE could define it focusing on achieving a balance between military requirements and humanitarian considerations, in alignment with the objectives of the CCW. Striking this balance is essential to ensure the active engagement of states that currently possess or utilize such weapons in the evolving legal framework. By fostering this equilibrium, the GGE could simultaneously advance the disarmament of AWS that could result in lethal effects that are indiscriminate or cause superfluous harm. At the same time, it could support the responsible integration of emerging technologies in AWS, which may enhance compliance with IHL.
