A few more thoughts on the feasibility question...
The short answer to “would a capture operation against al-Awlaki have been feasible?” is “Depends on the amount of risk and expense you’re willing to incur.” Both a drone strike and an SOF raid require the same basic priors: reasonably accurate knowledge of target location, and access to that location by air. An SOF raid is a more substantial undertaking because it requires more expensive aircraft, more personnel, and greater firepower. It also runs a significantly greater risk in terms of personnel and equipment; even if the enemy doesn’t shoot down the aircraft or resist on the ground very effectively, accidents happen a lot. An SOF raid can also require a more substantial diplomatic commitment. Even if Yemen and Pakistan are willing to tolerate drone raids, they may not want to host (however briefly) SOF. However, such reluctance is a manageable problem; better to ask forgiveness than permission, and a couple new F-16s heal all wounds, etc.
And so yes, in the literal sense a raid to capture al-Awlaki would have been feasible. But while it wouldn’t have been militarily or politically impossible to seize al-Awlaki in Yemen, it would be militarily impossible to conduct operations on the scale of the drone war without the drones. Special forces operations are much more costly, much more difficult, and consequently can be executed with much lower frequency than drone attacks. In areas where JSOC has dense infrastructure (bases) and legal impunity (a host government like Afghanistan), a large scale raid program is workable. In places like Yemen, Somalia, and Pakistan, you need drones in order to carry out a war of the scale that the Obama administration wants. SOF raids may be worthwhile for a few important targets (like bin Laden) but there’s a limit on how far you can scale that up.
And so the next question becomes “was al-Awlaki a special target by virtue of his American citizenship, or was he just another Al Qaeda operative?” If he’s special, then the feasibility question is important and relevant; it might be worthwhile to risk the cost and casualties to grab him. If he’s not special, then a grab operation isn’t feasible; if you allow that any old target requires the devotion of substantial SOF resources, then again its impossible to carry out the war that Obama has been waging.
Now I, for one, do think that al-Awlaki was special, or more specifically that the US government has special responsibilities to its citizens. First, a couple points to narrow the conversation and describe my priors. I don’t have any particular problem with the idea of being at war with an NGO, or with a collection of NGOs; the idea that “war” is only something that happens between sovereign states is a an artifact of how that particular form of social organization has come to dominant social life over the past century or so. Moreover, I much prefer the construction “we are at war with Al Qaeda” to “we are at War with Terror;” the former is a legal claim, while the latter is an absurdity. In the context of such a war, the drone campaign may or may not be appropriate. I’m inclined to think about this question from practical rather than legal grounds, mostly because the legal arguments are extremely complicated and are fuzzy/flexible; an institution as large as the executive branch of the United States government can effectively make many things legal, or at least legal enough to squeeze past a judiciary uninterested in constraining executive foreign policy-making power. The key question about the drone war, then, becomes “does it work?” The administration is certain that it does; I am less certain, but that’s a debate for another day.
But then, for the reasons I discuss in this thread, I do think that the US government has different ethical responsibilities to American citizens and non-Americans. In broad terms, the US government is expected to protect its citizens and respond to their needs; citizens of other countries make similar claims, at least theoretically, against their own governments. If the US kills a Saudi, at the very least it’s answerable to complaints from the Saudi government, even if in practice that government is unlikely to complain about most of the people the US wants to kill. US citizens are owed (morally, if not legally) an extra degree of consideration from the US government, to the extent at least of public evidence, actual indictments, and good faith efforts to capture rather than kill.
The issue of whether al-Awlaki merits the additional resources and risk that an SOF raid would entail thus becomes mainly political, with contributing legal and military considerations. And for all the justifications for not using special forces, I have no doubt that this one rang true for policymakers: “Why should we risk the lives of Navy SEALs to apprehend this asshole, whom we firmly believe to be guilty of terrorist activity? In weighing the lives of American citizens, why would we ever risk the former to save the latter?” This question has a political corollary, which runs “Why would we ever want to appear to be risking the lives of Navy SEALs to apprehend this asshole, who has no constituency beyond a bunch of hippies who hate us anyway?”
On its own terms, this political logic is extremely compelling. The Obama administration ran an enormous risk by sending such a large SOF team into Pakistan to kill bin Laden. If a helicopter had crashed, if bin Laden had escaped, or both, the administration would have faced some very serious problems both inside and outside of government. Mitt Romney et al would have demanded to know why Obama “let bin Laden get away” by not killing him with an airstrike, while the military and intelligence community would probably blame the administration for the failure of the mission. Obama decided this was worth the risk because the upside was so high; everybody would be happy if bin Laden was dead. With al-Awlaki and similar figures, the reward for even a successful capture isn’t that high. While evidence against al-Awlaki probably isn’t tainted to the same degree as figures apprehended during the Bush administration, it’s likely that the administration would still view a trial as politically and legally difficult. Even if you capture him, you lose; if you kill him while “trying” to capture him, the hippies are still unhappy; if SEALs die while trying to capture him, then Rick Perry complains about how your “law enforcement approach” to fighting the War on Terror is costing America the lives of its very best, etc.
This is enough to make you exceedingly receptive to arguments that it’s both legal and appropriate to blow up al-Awlaki rather than try to capture him. I hasten to add that what I’m trying to do here is give a notional description of the political decision-making process, rather than an apology for it; to the extent that decisions were made in order to avoid domestic criticism from one coalition, space obviously opens up for critiques from other coalitions. In this case, I suspect that assessments both of the political considerations discussed above (don’t risk SEALs, and don’t be seen as risking SEALs) weighed heavily on policymakers. Both represent tradeoffs, the former trading due process and robust protection of American citizens for risk to the lives of American soldiers, and the latter weighing Mitt Romney’s criticism against Glenn Greenwald’s.