The world is a better place with Anwar al-Awlaki and Samir Khan no longer around. Al-Awlaki was a principal figure in the Yemen-based group that calls itself al-Qaeda in the Arabian Peninsula, which in recent years has been the most active Sunni extremist band seeking to inflict harm on the United States. Al-Awlaki and Khan both were skillfully using their U.S. backgrounds to put lethal ideas in the heads of impressionable young American Muslims.

But if the killing of these men was solely a matter of acting upon these sorts of observations about dangers they posed, the killings would not be fundamentally different from many arbitrary, lethal actions taken by dictatorships who have perceived threats coming from expatriates. I have said that missile strikes from drones to eliminate individual terrorists are a tool that should not be removed from the counterterrorist tool kit, but that the criteria for designating and identifying targets need to be clearer than they have been. The difference between the United States and the dictatorships is that the United States requires something more, procedurally and legally, than mere observations by the executive authority that someone poses a threat. The foundation for that requirement is the clause in the Fifth Amendment to the U.S. Consitution that states that no person shall be deprived of life, liberty, or property without due process of law. The requirement is all the more acute with U.S. citizens, as both al-Awlaki and Khan were. What happened in Yemen on Friday was essentially a long-distance execution without judge, jury or publicly presented evidence.

The rationales that some have offered for dispensing with any more procedure than there was do not cut it. We hear that Awlaki renounced his U.S. citizenship. But U.S. law specifies a procedure, which involves appearing in person at a U.S. embassy or consulate and signing an oath of renunciation. I have heard nothing about Awlaki following that procedure, without which anything anyone says about renouncing citizenship has no legal effect. Then there is all the talk about people like Awlaki being at “war” with the United States. The war terminology has been applied to terrorism so loosely, for political and other purposes, for so long that it has lost whatever usefulness it might have had—and it probably didn't have any to begin with—for making procedural and legal distinctions in cases such as this. All sorts of individual miscreants and misfits declare “war” on their societies and countries. The one clear line that can be drawn about war concerns armed hostilities with another state—a line that is the basis for a whole body of international law. But short of that, the “war” talk is metaphorical mush.

President Obama on Friday described al-Awlaki as “the leader of external operations” for al-Qaeda in the Arabian Peninsula—the first time we have heard that description applied to al-Awlaki, despite plenty of earlier public attention to him. There was no more specific justification for that label. His main impact has been as a propagandist. In whatever role he played as an operational leader, he was more replaceable than as a broadcaster of ideas.

The issues may be even stickier with Samir Khan. It is unclear to what extent he was an intended target more than collateral damage in an operation aimed primarily at al-Awlaki. But insofar as his death could be seen to be highly likely in the strike against al-Awlaki, similar considerations ought to have entered into the decision making as if he had been the sole target. All available indications are that Khan was purely a propagandist. He produced the slick English-language magazine Inspire. His product was speech—hateful speech intended to inspire others to perform deadly acts—but still speech. And here is where we have to take extra care to distinguish what the United States did to him from many other instances in history of regimes killing expatriates merely because they felt threatened by what the expatriates were saying and writing. This includes the Islamic Republic of Iran's former habit of assassinating exiled political figures. It also includes numerous assassinations by the Soviets, perhaps most notably the murder with an axe of Leon Trotsky at the hands of an agent sent by Stalin.

We can distinguish the killings in Yemen from the murder of Trotsky by pointing to the particular motivations and political circumstances in each case, noting especially that the predominance of evil lay with Stalin, one of the biggest mass murderers in history. But assessing evil and the nobility or ignoble nature of motives is inherently subjective and thus subject to caprice and arbitrariness. More fundamental distinctions have to return to law and procedure. Probably more of a procedure lay behind the Yemen operation than behind Stalin's sending of the axe murderer—we hear some things about intra-administration drawing up of target lists for the drone operations—but we don't really know that.

The Yemen operation exemplifies how difficult it can sometimes be to reconcile certain objectives such as eliminating certified bad guys with other objectives or standards that are also very important, even if the damage from compromising them may not be immediately apparent. I do not presume to be able to determine exactly where the lines between the permissible and impermissible ought to be drawn, but I know that we need clearer lines than we have now.