In early 2024, reports emerged that several military forces were experimenting with brain-computer interfaces to enhance battlefield awareness and coordination.1 The U.S. military, for instance, has invested heavily in neurotechnology to allow soldiers to control drones and other machinery using only their thoughts.2 Similarly, China has been researching pharmaceutical enhancements to improve soldier endurance and cognitive function.3 These advancements are commonly known as military enhancement and illustrate how rapidly evolving technologies are reshaping modern warfare. The rise of these innovations raises critical questions about how such technologies should be regulated. In this context, international law plays a crucial role in ensuring that military enhancements comply with existing legal frameworks. This article will analyse whether current international law is adequate in addressing the future challenges posed by military enhancement. To do so, it will first define military enhancement before assessing its legality under the Geneva Conventions’ weapons review process. The primary legal questions at hand are whether military enhancement technologies can be classified as weapons under the Geneva Conventions and what the implications would be if the answer is affirmative.
What is military enhancement?
As a working definition of human enhancement, Dinniss & Kleffner’s definition will be used: “Human enhancement is the process of endowing an individual with an ability that goes beyond the typical level or statistically normal range of functioning for humans generally, where the ability is either integrated into the body or is so closely worn or connected that it confers an advantage similar to an internal or organic enhancement that transforms the person.”4
As such, military enhancement can be divided into three broad categories. Firstly, biochemical enhancement refers to the use of pharmaceuticals in order to enhance a person’s performance on the battlefield.5 One notable example is modafinil, a drug approved for military use in both the United States and France. Modafinil is known to promote wakefulness, enhance cognitive function, and improve focus, making it particularly useful for prolonged operations.6
Secondly, cybernetic enhancement refers to the connection of the human brain to a machine. This emerging technology enables direct brain-machine interfaces, allowing soldiers to control external systems, such as drones, robotic units, and other autonomous platforms, through neural signals.7 Additionally, cybernetic enhancements can assist in rapid data analysis and decision-making by enabling individuals to process vast amounts of information more efficiently.8 While still in the early stages of development, advancements in neural implants and artificial intelligence suggest that cybernetic enhancements could play a crucial role in future military operations.
Finally, prosthetic enhancement involves the addition of advanced physical augmentations to the human body. While traditionally used to replace lost limbs, modern prosthetic technology is evolving beyond simple restoration. For instance, advanced bionic eye implants may enhance vision by providing night vision capabilities or the ability to detect infrared or thermal signatures. Similarly, brain-connected targeting systems could allow soldiers to aim and fire weapons with increased accuracy and reduced reaction time.9
The integration of these advanced technologies into military operations raises significant legal questions under international law, particularly in relation to the law of armed conflict. Given the rapid advancements in military enhancement technologies, it is crucial to examine how these innovations align with existing legal norms and to assess the extent to which they are permitted under the current legal framework.
Military enhancement as weapons
While various legal instruments, including the Hague Conventions and multiple other weapons conventions, may play a role in regulating military enhancement technologies, this article will focus on the Geneva Conventions, particularly Article 36 of Additional Protocol I.10 Although not all states, such as the United States, are parties to Additional Protocol I, many have adopted similar review mechanisms to assess the legality of emerging military technologies.11
Under article 36 of the Additional Protocol I, state parties are required to determine whether the use of a specific weapon is prohibited under international law. It is important to note here, however, that it is the employment of such weapons that will trigger the obligation to perform a weapons review, not the mere possession.12 The key question here is whether military enhancement technologies qualify as a “weapon, means, or method of warfare”.13 While the Protocol does not provide a specific definition for the key elements associated with weapons, nor do other international legal instruments, commentators have identified two primary characteristics that define a weapon. First, a weapon must possess the capability to cause direct harm, meaning it has the potential to inflict injury or damage to individuals or objects. Second, a weapon is typically characterised by its status as an object utilised by an agent, such as a soldier or a machine, to achieve a specific military purpose. 14
Under this definition, it is challenging to categorise military enhancements within the existing classifications outlined in the Protocol. For instance, an integrated firearm within a prosthetic limb would likely qualify as a weapon, given that it has the capability to cause direct harm and is an object employed by an agent. In contrast, pharmaceutical enhancements do not fit this definition, as the drug itself does not directly cause harm. Rather, it is the soldier's use of the drug that may lead to harm. It is also important to note that human soldiers have historically never been defined as weapons and, as such, are not subject to weapons reviews.15 However, some scholars argue that an enhanced human soldier might eventually be classified as a weapon if the enhancements are far reaching enough.16 As a result, it remains uncertain whether military enhancement can be classified as a weapon, and as such are subject to a weapons review. Nonetheless, the requirements established for the weapons review will be explored to gain a clearer understanding of its suitability for evaluating military enhancement technologies.
The weapon review of art.36
For the weapons review, Article 36 of the Additional Protocol I sets out 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.” In order to determine whether this is the case, historically, it has been established that new weapons need to conform to the principles of distinction, proportionality and the prohibition on superfluous injury or unnecessary suffering.17
Firstly, the principle of distinction mandates that a weapon must be precise enough to target only combatants and must never deliberately harm noncombatants. This ensures that the use of force remains directed solely at those engaged in hostilities.18 Regarding the principle of proportionality, any weapon used must be proportionate to the military objective it aims to achieve, meaning that the harm caused to civilians and civilian objects should be minimised.19 Finally, the prohibition on superfluous injury aligns with proportionality, as it asserts that any method of attack must cause no more harm than necessary to incapacitate a combatant.20 This principle has led to the banning of certain weapons, such as poison21 or blinding lasers22, due to their excessive and unnecessary harm.
Taking the example of brain-computer interfaces, where the brain is connected to an external weapon, illustrates the difficulty of applying these principles in the area of military enhancement. One might argue that this instrument does not raise substantial concerns, as long as the decision to fire remains with a human operator. However, several potential evolutions of this technology could create problematic situations. For instance, the development of a weapon that automatically engages targets when brain signals detect a perceived threat. This raises critical ethical questions: what occurs when a neural interface is configured to fire at the head or chest rather than aiming for non-lethal methods? Such a device would be designed with the intent to kill, violating the principles of proportionality and non-superfluous injury.23
On the other hand, the use of brain-computer interfaces actually have the potential to improve compliance with the rules of distinction and proportionality in military operations. By enhancing accuracy in targeting, these technologies could help ensure that combatants are more effectively distinguished from noncombatants, thereby minimising the risk of civilian casualties. Furthermore, this technology could help reduce fatigue-related problems that often affect operators, who typically analyse images and make critical decisions over extended periods.24
In the case of biochemical enhancement, the assessment of compliance with the principles of the weapons review can be approached similarly. While certain drugs may lead to adverse effects, such as inducing extreme violence in soldiers, which could result in injuries that violate the prohibition on superfluous injury, there are also potential benefits to consider. For example, some drugs may help reduce fatigue among soldiers, thereby improving their performance and decision-making in high-pressure situations. This could contribute to better adherence to the principles of proportionality and distinction.
This illustrates that applying the current principles of the weapons review to the case of military enhancement does not yield a definitive answer. Firstly, it remains unclear whether military enhancements would even qualify as weapons under the definition provided in Article 36. If they are deemed to fall within this category, it is uncertain how the established principles of distinction, proportionality, and the prohibition on superfluous injury should be directly applied to them. Additionally, due to the lack of legal precedent on this topic, it is unclear how international courts perceive this issue.
The potential implications of these technologies for both combatants and civilians underscore the urgent need for a legal review mechanism specifically tailored to address the complexities associated with military enhancements. Therefore, in light of the previous analysis, I believe it is essential to either revise the existing principles of the weapons review to accommodate the challenges posed by future military enhancements or to establish a new category within the weapons review altogether. Such measures would ensure that international law remains effective in regulating the use of emerging technologies in armed conflict.
1 U.S. Department of Defense. (2024). Military and security developments involving the People’s Republic of China: Annual report to Congress.
2 Kosal, M., & Putney, J. (2023). Neurotechnology and international security: Predicting commercial and military adoption of brain-computer interfaces (BCIs) in the United States and China. Politics and the Life Sciences, 42(1), 81–103. https://doi.org/10.1017/pls.2022.2
3 U.S. Department of Defense. (2024). Military and security developments involving the People’s Republic of China: Annual report to Congress.
4 Harrison Dinniss, H. A., & Kleffner, J. K. (2016). Soldier 2.0: Military human enhancement and international law. International Law Studies, 92, 432.
5 Harrison Dinniss, H. A., & Kleffner, J. K. (2016). Soldier 2.0: Military human enhancement and international law. International Law Studies, 92, 432
6 Van Puyvelde, M., et al. (2022). A state-of-the-art review on the use of modafinil as a performance-enhancing drug in the context of military operationality. Military Medicine, 187(11–12), 1286–1298
7 Harrison Dinniss, H. A., & Kleffner, J. K. (2016). Soldier 2.0: Military human enhancement and international law. International Law Studies, 92, 432.
8 Sharp, A. (2023). Understanding future human cybernetic integration: A framework to map enhancement technologies. Computers in Human Behavior: Artificial Humans, 1(2), 100029.
9 Harrison Dinniss, H. A., & Kleffner, J. K. (2016). Soldier 2.0: Military human enhancement and international law. International Law Studies, 92, 432
10 Lin, P., Mehlman, M., Abney, K., French, S., Vallor, S., Galliott, J., Burnam-Fink, M., LaCroix, A. R., & Schuknecht, S. (2015). Super soldiers: The ethical, legal, and operational implications. https://doi.org/10.4018/978-1-4666-8195-8.ch074
11 Harrison Dinniss, H. A., & Kleffner, J. K. (2016). Soldier 2.0: Military human enhancement and international law. International Law Studies, 92, 432.
12 Blake, & Imburgia, J. S. (2010). Bloodless weapons? The need to conduct legal reviews of certain capabilities and the implications of defining them as weapons. Air Force Law Review, 66, 168.
13 International Committee of the Red Cross. (1977). Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I), Article 36. International Legal Materials, 16, 1391. https://ihl-databases.icrc.org/en/ihl-treaties/api-1977/article-36
14 Chengeta, T. (2016). Are autonomous weapons systems the subject of Article 36 of Additional Protocol I to the Geneva Conventions? U.C. Davis Journal of International Law & Policy 23(1), 65–100.
15 Chengeta, T. (2016). Are autonomous weapons systems the subject of Article 36 of Additional Protocol I to the GGeneva Conventions? U.C. Davis Journal of International Law & Policy, 23(1), 65–10
16 Lin, P. (2013, January 4). Could human enhancement turn soldiers into weapons that violate international law? The Atlantic.
17 Harrison Dinniss, H. A., & Kleffner, J. K. (2016). Soldier 2.0: Military human enhancement and international law. International Law Studies, 92, 432.
18 Shereshevsky, Y. (2021). Are all soldiers created equal? On the equal application of the law to enhanced soldiers. Virginia Journal of International Law, 61(2), 271–324.
19 Moulin, T. (2022). No more humans? Cybernetically-enhanced soldiers under the legal review of Article 36. Journal of Law & Cyber Warfare, 8(2), 59–104.
20 Liu, Y. (2022). Regulating the use of military human enhancements that can cause side effects under the law of armed conflict: Towards a method-based approach. National Security Law Brief, 13, 29.
21 Lieber Code. (1863). Article 70. In Instructions for the Government of Armies of the United States in the Field (Vol. II, Ch. 21, § 4). Hague Regulations. (1907). Article 23(a). In Regulations respecting the Laws and Customs of War on Land (ibid., § 2). International Criminal Court. (1998). Article 8(2)(b)(xvii). In Rome Statute of the International Criminal Court.
22 United Nations. (1995). Protocol on blinding laser weapons (Protocol IV of the 1980 Convention on Certain Conventional Weapons). https://www.un.org/en/genocideprevention/documents/atrocity-crimes/Doc.43_CCW%20P-IV.pdf
23 Moulin, T. (2022). No more humans? Cybernetically-enhanced soldiers under the legal review of Article 36. Journal of Law & Cyber Warfare, 8(2), 59–104.
24 Moulin, T. (2022). No more humans? Cybernetically-enhanced soldiers under the legal review of Article 36. Journal of Law & Cyber Warfare, 8(2), 59–104.
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