A few thoughts on the US assassination of Anwar al-Awlaki:al-Awlaki was an al-Qaeda leader with American citizenship, and he (probably) was recently killed by a US drone strike in Yemen. His death, absent a trial (and with requests by charitable groups to legally represent him denied), is controversial.
I believe that his assassination is acceptable, for largely the same reasons that it was acceptable to kill Osama bin Laden.
I don't believe that it is significant that he was a US citizen. In general, unless there is a very strong interest, the US should not be assassinating people regardless of their citizenship, and I believe that most of the jurisprudential protections afforded citizens WRT US actions should also be afforded non-citizens. We do these things generally because we believe that's what it means to be civilised, not because we're trying to establish a perk for citizens.
I am further unbothered at the idea that this will set precedent or erode a cherished habit. American traditions of justice are important and generally pretty decent, but they happen in the legal context of a nation with effective control over its own territory (or in cases of extradition, having a gentleman's agreement with an effective state to mutually retrieve criminals-for-certain-kinds-of-crime with help from each other's land). In areas where the US is unable to use state power to safely capture criminals, either in the midst of insurrection or when dealing with hostile or failed states (Yemen is closer to the latter), if it lacks the ability to surely and effectively capture someone who poses an existential threat to the US, I believe it is acceptable to kill them as an alternative. This is a corner case, very difficult from our general system of jurisprudence.
With rare exception(*), our traditions and values should not amount to a suicide pact. The duty of a government to protect its people from aggression is a higher one than any duties its constitution might put upon it.
(*with the main thrust of the argument over, I provide two examples of cases where I hold that we must hold to principles even if they do amount to national suicide: a nation must not tell big lies about its history and demand fealty to them, and a nation must never conduct/arrange torture; nations that do these things do not merit respect and should be replaced with nations that abstain from them. Likewise, I hold that it is always acceptable (and amounts to a strong should) to kill to prevent torture, most ideally those who command or conduct the torture but less ideally the would-be victims. Those who command or conduct torture should be considered beyond the pale )