There's a lot to discuss about the OLC memo on the al-Aulaqi strike---including, as Ben mentioned yesterday, the origins and significance of "imminence." (There's also excellent analysis over at Just Security, which I recommend to interested readers.)
Throughout the OLC memo's 41 pages, the much-scrutinized term appears several times, often as part of a phrase: "continued and imminent." This was borrowed from an unknown source---we can't identify one, because of redactions---and seemingly meant to characterize the danger al-Aulaqi posed. On page 21, for example, the memo says executive branch personnel had concluded that al-Aulaqi's activities "pose a 'continued and imminent threat'" to U.S. persons and interests. On page 39, the memo also says that, on the facts represented to its authors, "a decision-maker could reasonably decide that the threat posed by al-Aulaqi's activities to United States persons is "continued" and "imminent."" I count three other mentions of the "continued and imminent" language elsewhere in the document, too.
And yet, in all of the OLC memo's unredacted parts, we find neither analysis of the requirement, nor an explanation of its provenance. That puzzle lead Ben to advance his hypothesis about how "imminence" found its way into the OLC memo, and thus into other government documents drawn from the memo:
Warning: From here on in, I am speculating, and I could well be wrong. But I think the source of law for imminence in Holder’s speech, in the white paper, and in this memo is a presidential covert action finding. That is, I think the president, in issuing whatever finding gave rise to the killing of Al-Aulaqi, limited the authorization to situations involving imminent threats. This invocation was prudential, not legally required by any other source of law, but it operates as law for the executive branch.
I think Ben is likely right---or at least, there's evidence to support his claim. But before elaborating further, let me acknowledge that I, like Ben, will be engaging in some speculation for a moment; and that I, like Ben, might be dead wrong about what follows. With that caveat made, here is some reporting consistent with Ben's theory.
In this 2010 Washington Post story, Dana Priest described the Obama Administration's targeted killing operations in Yemen. Along the way, Priest also set out some historical background, including this little nugget about the Bush Administration's post-9/11 legal moves:
[CIA Director George] Tenet provided [Yemeni President Ali Abdullah] Saleh's forces with helicopters, eavesdropping equipment and 100 Army Special Forces members to train an antiterrorism unit. He also won Saleh's approval to fly Predator drones armed with Hellfire missiles over the country. In November 2002, a CIA missile strike killed six al-Qaeda operatives driving through the desert. The target was Abu Ali al-Harithi, organizer of the 2000 attack on the USS Cole. Killed with him was a U.S. citizen, Kamal Derwish, who the CIA knew was in the car.
Word that the CIA had purposefully killed Derwish drew attention to the unconventional nature of the new conflict and to the secret legal deliberations over whether killing a U.S. citizen was legal and ethical.
After the Sept. 11 attacks, Bush gave the CIA, and later the military, authority to kill U.S. citizens abroad if strong evidence existed that an American was involved in organizing or carrying out terrorist actions against the United States or U.S. interests, military and intelligence officials said. The evidence has to meet a certain, defined threshold. The person, for instance, has to pose "a continuing and imminent threat to U.S. persons and interests," said one former intelligence official.
The Obama administration has adopted the same stance. If a U.S. citizen joins al-Qaeda, "it doesn't really change anything from the standpoint of whether we can target them," a senior administration official said. "They are then part of the enemy."
The next-to-last paragraph (to which I have supplied emphasis) doesn't mention any covert action finding. But it hints in that direction, with its "Bush gave the CIA ... authority to kill U.S. citizens abroad" language. Moreover, "one former intelligence official" also said that, under Bush's instructions, a U.S. citizen would have to pose a "continuing and imminent threat to U.S. persons and interests," before the government could use lethal force. That doesn't perfectly match the OLC memo's "continued and imminent" threat language---but it sure comes pretty close to doing so.
All of which is to say: Ben's theory might well be correct. On one reading of Priest's reporting, President Bush could have established something quite like the "continued and imminent" criterion, in a finding made under the covert action statute. That in turn might have lasted into the Obama administration---and informed the al-Aulaqi OLC memo.