So I think it's important to acknowledge that in his response, Ben Wittes isn't arguing, simply, that the president has the authority to kill anyone suspected of terrorism under any circumstances. He's arguing that authority is more narrow (emphasis original):
The real dispute centers around the targeting of a U.S. national in zones at once outside of conventional military battlespaces and outside of the reach of law enforcement. Yet the real dispute is narrower even than this. Because if Anwar Al Aulaqi were merely suspected of being a serial rapist and murderer, I would have no reservations about saying that the President lacks any authority to target him even in ungoverned areas of Yemen. That is, when the criminal makes it to an ungoverned space, he wins. We don’t get to follow him there with a Predator. So the real authority is limited not just by geography and governance but by the nature of the target himself. That is, the president may only target an American national when when he has concluded in good faith that this person is either covered by the AUMF or poses a sufficiently-immediate threat to the country so as to trigger its right to self-defense.
Look, I'm going to freely acknowledge that for the most part, liberals are indifferent to the forward march of the imperial presidency. But for the civil libertarian left, the story of the last few years isn't one about Republicans lying about intelligence or matters of national security, it's about the government lying about intelligence and national security. Looking back at matters like the threat of a "mushroom cloud" to justify support for war in Iraq, and the insistence that the hundreds of people who were released without charge from Gitmo despite being tagged "the worst of the worst" mean that you simply cannot take the government's word for it. So even if one believes the evidence against al-Awlaki to be persuasive, the fact is most Americans found the rationale for war in Iraq persuasive. Most Americans are frightened enough of the unconvicted detainees at Gitmo that they can't stomach them being placed in a federal prison on American soil. We are dealing with a genuinely difficult dilemma here--an enemy force that doesn't wear uniforms and isn't easy to identify. Which is why it's so important to get it right.
The fact is that recent years have proven that even if the executive has the best interests of the American people in mind, terrifying intelligence information that seems conclusive at one moment becomes disastrously false the next. As with war in Iraq, the deaths that result from those erroneous conclusions is, unlike detention, completely irreversible. For that reason, folks on the civil libertarian left--and the genuinely small government right--think that granting a secret, unreviewable power of life and death over American citizens, even in the limited circumstances Wittes describes--and I think history has shown that the limits on those circumstances rarely last--is unconscionable.
