When drones, or unmanned combat air vehicles, carry out targeted assassinations are they covered by existing laws for armed conflict? After all, combatants are accustomed to ‘an equal right to kill’, Grégoire Chamayou explains, and ‘if one has the right to kill without crime, it is because that right is granted mutually’.

But drones, the author argues, deprive one combatant of this notion of armed equality and, moreover, deny them self-defence, or ‘a right to the chance of combat’. In the absence of traditional reciprocity, warfare ‘degenerates into a putting-to-death’.

But there could be a ‘third legal way’, suggests Kenneth Anderson, a visiting fellow at the Hoover Institute –‘a new regime of ad hoc law for these death-dealing operations’. This ‘curious legal hybrid’ would at least confer legitimacy on militarised manhunting.

Another problem, warns Chamayou, a research scholar in philosophy at the Centre National de la Recherche Scientifique, is that drones might encroach illegally into zones of peace to execute suspects, ‘redefining the notion of armed conflict as a mobile place’.

Author: Grégoire Chamayou

Publisher: Penguin (£6.99)

In Drone Theory, jurist Mary Ellen O’Connell maintains that drone strikes in Pakistan, Somalia and Yemen were illegal because they took place outside the scope of armed conflict that legitimises the use of battlefield weapons, and ‘therefore constitute grave violations of the laws of war’.

In a chapter titled ‘Precision’, Chamayou points out that the law on armed conflict ‘prohibits the direct targeting of civilians’, and acknowledges that the drone has been praised for identifying the difference between combatants and non-combatants. But if the drone has already negated the traditional concept of hostilities, where troops are on the ground pointing their weapons, then the definition of a combatant posing an immediate threat no longer exists.

Chamayou is particularly thought-provoking on who or what would be held responsible if a robot committed a war crime. The state that owns the drone, the military commander, technicians and manufacturers might all direct blame at one another. Ultimately, the drone itself could be on trial, and here he cites the bizarre example from 1386 when infanticide in a village in Calvados led to a ‘criminal’ sow being executed.

Away from the battlefield, Chamayou considers whether drones could be defined as instruments of law enforcement. Legal scholar Laurie Blank stresses that enforcement authorities must only use the degree of force necessary to make an arrest and that ‘the use of lethal force should remain the exception’. Drones are clearly incapable of doing that as it is ‘either shoot to kill or take no action at all’.

Chamayou’s book is required reading for all those with an interest in how modern weaponry is rewriting the laws of warfare.

Nicholas Goodman is a sub-editor at the Gazette