Just so, there may be occasions when a dangerous international enemy is vulnerable, the danger is immediate, and the government has a clean shot. Even if that enemy is an American citizen, the Constitution is not offended if government pulls the trigger.
But there are two differences between Awlaki and Dykes. First, in the case of Dykes, FBI officials will conduct an after-the-fact executive-branch investigation of the agents' acts. Those who ordered and used deadly force will be accountable to an administrative board that was not involved in the decision. An official report will determine credit and blame; and under proper circumstances, that report will be available to courts, Congress, and the public.
Second, Dykes's heirs, if there are any, can bring a lawsuit in federal court. They can get information and testimony from the government. If they prove the killing was improper, they may get damages. But even if they fail, Dykes had a day in court and the government was called to account.
These two mechanisms of accountability seem to be missing from the current drone-strike program. Before Awlaki was killed, his family had asked a federal court to block the attack; the case was dismissed. Now the survivors are suing in federal court for wrongful death. The administration argues that the issue is a "political question" entirely beyond the reach of the courts.
Attorney General Holder has said that the decision to order lethal drone attacks receives "a thorough and careful review"; the white paper says only that a strike is carried out "where an informed, high-level official of the U.S. government has determined that the targeted individual poses an imminent threat of violent attack against the United States." As generalities, these aren't even very soothing: "Don't worry, we only kill bad guys, and we know 'em when we see 'em."
Sometimes -- as in some international version of the Dykes case -- there isn't time for procedures beforehand. OK, then, what about review afterwards? As the administration sees it, neither before nor after is there to be any review outside the executive branch. The courts can't intrude, and Congress will only be be "notified," and only afterwards.
What about within the executive branch?
On this point, the tone of the speeches and the "white paper" remind me of the revenge drama in Thomas Pynchon's The Crying of Lot 49: "[A] new mode of expression takes over. It can only be called a kind of ritual reluctance. Certain things, it is made clear, will not be spoken aloud ..."
There is no hint that after-the-fact executive-branch review is important. There is no commitment to carry it out. There is no discussion of procedures to do it. In fact, the universe apparently contains no such concept. Once the Hellfire missile falls out of the sky, both the dead and the decision to kill them vanish in the flames.