Should enhancement technologies -- which typically do not directly interact with anyone other than the human subject -- be nevertheless subject to a weapons legal-review? That is, is there a sense in which enhancements could be considered as "weapons" and therefore under the authority of certain laws?

In international humanitarian law (IHL), also known as the laws of war, the primary instruments relevant to human enhancements include: Hague Conventions (1899 and 1907), Geneva Conventions (1949 and Additional Protocols I, II, and III), Biological and Toxin Weapons Convention (1972), Chemical Weapons Convention (1993), and other law. Below, I discuss these agreements and what their implications may be for human enhancement.

1. Would human enhancements count as weapons under the Geneva Conventions?

Let's start with the basic requirement that new weapons must conform to IHL. Article 36 of the Geneva Conventions, Additional Protocol I of 1977, specifies:

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.

But does Article 36 apply to human enhancement technologies? That is, should they be considered as a "weapon" or "means or method of warfare" in the first place? Unlike other weapons contemplated by IHL, enhancements usually do not directly harm others, so it is not obvious that Article 36 of Additional Protocol I would apply here. If anyone's safety is immediately at risk, it would seem to be that of the individual warfighter -- thereby turning the debate into one about bioethics. To that extent, warfighters, whether enhanced or not, are not weapons as typically understood.

Yet in a broader sense, the warfighter is not only a weapon but perhaps a military's best and oldest weapon. Warfighters carry out missions, they sometimes kill enemies, and they represent one of the largest expenditures or investments of a military. They have cognitive and physical capabilities that no other technology currently has, and this can make them ethical, lethal, and versatile. The human fighter, engaged in hand-to-hand combat, would be the last remaining weapon when all others have been exhausted. So in this basic sense, the warfighter is undeniably a weapon or instrument of war.

If a military were to field a weaponized rhino in an urban battlefield that contains innocent civilians, we would be reasonably worried that the war-rhino does not comply with Article 36. Are weaponized humans any different, legally speaking?

Still, should Article 36 be interpreted to include warfighters themselves as weapons subject to regulation? There could be several reasons to think so. First, other organisms are plausibly weapons subject to an Article 36 review. Throughout history, humans have employed animals in the service of war, such as dogs, elephants, pigeons, sea lions, dolphins, and possibly rhinoceroses. Dogs, as the most commonly used animal, undergo rigorous training, validation, and inspections. If a military were to field a weaponized rhino in an urban battlefield that contains innocent civilians, we would be reasonably worried that the war-rhino does not comply with Article 36. If rhinos cannot reliably discriminate friends from foe, e.g., a rhino may target and charge a noncombatant child in violation of the principle of distinction. A similar charge would apply to autonomous robots in such a general environment in which distinction is important, as opposed to a "kill box" or area of such fierce fighting that all noncombatants can be presumed to have fled.