The doctrine of proportionality has long been a part of governing the use of force under international law. It is understood to mean that the harm likely to be caused by the proposed action (in the case of drones, a targeted strike which is likely to result in the deaths of one or more people) must be “proportional” to the threat that the intended target poses. The application of the long established doctrine in non-battlefield situations, however, raises many practical questions.

In certain situations, the doctrine should not be difficult to apply. For example, if the feared harm is an imminent attack on a large civilian population, then the use of a precision weapon targeted at the leaders actively involved in the attack would seem to meet the proportionality standard.

However, other circumstances present difficulties in applying this doctrine. Consider the hypothetical that a confirmed senior Al Qaeda official is spotted by a Predator drone. The official has been difficult to locate, and while he does not pose any immediate threat, U.S. officials cannot be sure that it can find him again before the threat becomes imminent. Therefore, the situation represents a window of last opportunity. This situation seems relatively straightforward as a justified targeting if the U.S. chose to do so. However, add to the hypothetical that the official is on the same compound as a number of women and children who have no known Al Qaeda connections.

So consider these questions:

  • Is the death of the innocents acceptable under the doctrine of proportionality?
  • Is the level of collateral damage that  is acceptable influenced by the either the imminence or scope of the threat posed by the Al Qaeda leader?
  • Who is qualified to make the decision on proportionality and the acceptable collateral damage in such a situation?
  • Is the legal equation altered if the number of innocents is greater or lesser?