in that the interpretation of the specific content of the law is prone to change over time. Still, the point remains that Article 23 stands as a paradigm case of the interdependence of laws in governing conduct in war, and probably in governing conduct in most other legal contexts as well.22
A further difficulty for law-following is that legal contents may come into conflict with one another in ways that are conceptually difficult to resolve. Granted, law is generally hierarchical, but it is not always evident which guidance ought to take precedence in a particular case. For example, Convention I of the 1949 Geneva Convention, which addresses "the Amelioration of the Condition of the Wounded and Sick in Armed Forces in the Field." Convention I, Article 38 establishes the red cross and red crescent as markings identifying medical personnel and vehicles as prohibited targets and even prohibiting their improper use. However, it has not been uncommon during counter-insurgency operations to allow for the engagement of unmarked civilian vehicles, even where those vehicles appear to be providing life-saving medical care. This means that rules of engagement have often allowed soldiers to engage vehicles providing medical care on the legally justifiable grounds that they were not prohibited targets. Nevertheless, those vehicles would seem to satisfy the moral justification for the establishment of Article 38 in the first place (that is, the amelioration of the condition of the wounded and sick in armed forces in the field). It seems clear that reconciling a law that establishes protected status for medical personnel in war with a local rule allowing soldiers to target unmarked vehicles that may be performing a medical function depends on more than just the laws. It also depends on the context surrounding the application of those laws, a fact which applies to the law in general, but seems especially germane to resolving military law. The practical reality is that unmarked vehicles have often been used tactically to recover valuable weapons
22 It was brought to my attention during a presentation on this topic at the International Society of Military Ethics Conference in 2022 that Article 37 of the Geneva Convention (1949) prohibiting acts of perfidy offers an equally compelling example. The interpretation of prohibitions on perfidy depends at least as heavily on other law as the prohibition on assassination. I suspect that there are many and possibly better or more impactful cases than the one that I have identified here.
and intelligence from engagement sites, meaning that the rules of engagement—as they always do—reflect an effort to strike a balance between mission considerations and humanitarian concerns. Whether the rules of engagement strike the appropriate balance between those considerations is always a question worth entertaining—to quote John Austin, "the existence of law is one thing; its merit or demerit is another"23—but, the difficulty for law-following is that those considerations may be weighted differently at different levels of legal authority.
All of this serves simply to emphasize the more general point that following the laws of war depends on much more than any law in isolation. To the contrary, following the law requires an agent to reason prospectively about how the rules obligate and constrain legal subjects, and to reconcile any given application of those rules with relevantly similar past cases, a kind of judgment that John Rawls describes as reflective equilibrium. Put another way, the law follower needs to strike an adequate balance between understanding of the law and understanding of specific applications of the law. The difficulty for LAWS is that this type of consistency depends on an agent's ability to recognize and apply different types of rules in a loose hierarchy, to navigate the semantic content of those rules, and to reconcile those rules against countless other rules and cases. These challenges may not be irresolvable at least to the extent that nature has resolved them in human beings, but from the perspective of artificial intelligence the challenges are nevertheless substantial.
The Compliance Argument
I have argued here that following the law is actually far more demanding than one might assume and as a result, the technological bar to lethal autonomy is likewise higher than many people might have supposed. However, there is a compelling objection to this way of thinking about LAWS that deserves some attention. Arkin's claim is that engineers morally ought to build LAWS that follow the law, but maybe I have interpreted his claim too literally. Maybe what one ought to care about for LAWS is merely that they act in compliance with the law. Put another way,
23 John Austin, The Province of Jurisprudence Determined and The Uses of the Study of Jurisprudence, London, UK: Weidenfeld and Nicolson 1954, p. 184.
