"Not all strikes are individually targeted. The administration also uses “signature strikes” to target and kill groups of men who are not personally identified but appear to be hostile militants. While such a strategy might make sense on hot battlefields, where one frequently kills “the enemy” without knowing precisely who they are, it is extremely dangerous when employed beyond battlefields, where it can be very difficult to know with any degree of certainty which groups are engaged in hostile military action. For this reason, Obama initially banned such strikes in Yemen, but news accounts indicate that he has relaxed that ban recently. What criteria are used to distinguish the enemy from those who merely look like the enemy? As President Bush showed us, it’s all too easy to make mistakes in identifying the enemy. A mistakenly detained man can be released, as hundreds held at Guantánamo have been. Mistakes in the drone program are final."