My goodness, the amount of pseudo-informed drivel that oozes out of the majority of American's mouths makes me sick. How easy it is for you and your politicians to jump to conclusions without reading the fine print.
A more thorough discussion of this issue can actually be found in this thread. If you are truly open to the idea of fact-checking and logical explanation/elaboration, I suggest you join us there. However, I will still give you the introduction to my stance here, to save time and also engage more people in the debate. Regarding the actual official statements and implications on this issue:
It astounds me to see how many people are so willing to demonize even the slightest glimpse of executive power when given the opportunity. Please recognize the context and circumstances under which a lethal operation would be deemed necessary. (reference)
1) An informed, high-level official of the US government has determined that the target individual poses an imminent threat of violent attack against the United States.
I believe it is abundantly clear that these attacks would not be authorized for "passive" threats. In other words, simply being a member of a major terrorist organization would not justify this action. A specific individual - American or otherwise - must be presenting a threat that demands an immediate, effective response. A common argument is that terrorism is simply a form of criminal activity and can not be treated as a war entity. To this I say, law enforcement has been taking immediate, decisive actions in order to save lives for decades. I rarely ever hear complaints about SWAT operations or sharpshooters taking action after exhausting all other resources - especially when a criminal (American citizen, by the way) has taken hostages. The white paper is clearly specifying situations such as these, but on a national level. The target member of Al Qaeda must be an active threat.
2) Capture is unfeasible, and the United States continues to monitor whether capture becomes feasible.
Continuing from my previous statements and analogy, the threat presented by the target must be similar to having a finger on a trigger with the barrel aimed at the head of a hostage. If plans to rescue the hostage by killing the criminal are underway, the procedure can and should be aborted if the target exhibits a vulnerability that does not require lethal force. This is a basic synopsis of the "who" and "when" of targeted killing. An operation of this nature would only be considered as a last resort.
3 ) The operation would be conducted in a manner consistent with applicable law of war principles.
While the military has seen less than complimentary press about missed airstrikes and high collateral damages, it should be reasonable to assume that the United States would carry out this procedure intending to use the absolute minimum required force to successfully nullify the immediate threat. What we must understand is that war will never be fair - innocent lives will always be lost, and mistakes will be made by humans. There has been and will always be cases where operators receive incomplete or incorrect intelligence; however, while the possibility of misjudgment should be diminished by the best of our ability, the fear of it should certainly not prevent us from taking action.
I would also like to draw your attention to the first paragraph on page 3 of the pdf:
"Any operation of the sort discussed here would be conducted in a foreign country against a senior operational leader of al-Qa'ida or its associated forces .... The Supreme Court has held that the military may constitutionally use force against a U.S. citizen who is a part of enemy forces."
Unless you are an advocate of letting innocent people die in vital situations demanding immediate action, this idea of drone strikes on highly dangerous criminals is far from unreasonable.