Because "assassination" is a loaded term.

The US attorney general, Eric Holder, said the decision to kill a US citizen living abroad who poses a terrorist threat "is among the gravest that government leaders can face", but justified lethal action as legal and sometimes necessary in the war on terror.

Holder's comments on Monday broke the administration's silence on the legal justification for its decision to kill US-born al-Qaida operative Anwar al-Awlaki five months ago in Yemen.

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"The unfortunate reality is that our nation will likely continue to face terrorist threats that at times originate with our own citizens," Holder told a packed Thorne Auditorium.
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Al-Awlaki's killing in a joint CIA-US military drone strike on a convoy in Yemen sparked a public debate over whether the president should have the authority to kill an American citizen without a conviction and despite an executive order banning assassinations - which Holder called a "loaded term" that doesn't apply in this case.
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"Any decision to use lethal force against a United States citizen - even one intent on murdering Americans and who has become an operational leader of al-Qaida in a foreign land - is among the gravest that government leaders can face," Holder said. "The American people can be - and deserve to be - assured that actions taken in their defense are consistent with their values and their laws."

Unfortunately, the Administration won't release its legal justification for this targeted kill/assassination, so it's a little hard to be assured that it's consistent with the law. That's really my main issue. Mebbe they had sensitive information they needed to keep secret prior to the operation. But now that it's done, shouldn't we at least get to hear the reasons why they felt it was ok to go ahead and kill this guy who also happened to be a U.S. citizen?

And don't give me that "we're at war with the terrorists" schtick again, using that to justify every questionable action. If you felt you needed to do what you did, but it was not necessarily a "good" thing, you still need to own up to it. You shouldn't be allowed to cloak it with the "we're at war" blanket and feel no other justification is necessary.

Back in 1993, a guy from Kuwait planned and executed the 1993 bombing of the World Trade Center. We found the guy, captured him, extradited him, and tried him in a NY District court, and he wasn't a citizen. When did we stop doing that? When did the solution to everything become "shoot it, bomb it"? I love Hawkgirl, i really do, but even i know in real life you can't solve every problem by smashing it with your electrified mace.

This guy was probably a bad guy. He probably deserved to get shot in the head. I still would like my government to show me proof of that. I'd still like to know that the government and i are on the same page as to what constitutes a "bad guy".

Hina Shamsi of the American Civil Liberties Union:

"Few things are as dangerous to American liberty as the proposition that the government should be able to kill citizens anywhere in the world on the basis of legal standards and evidence that are never submitted to a court, either before or after the fact," Shamsi said. "Anyone willing to trust President Obama with the power to secretly declare an American citizen an enemy of the state and order his extrajudicial killing should ask whether they would be willing to trust the next president with that dangerous power."

With lines like these coming out of the Attorney General's mouth:

"The constitution guarantees due process, not judicial process."

I'm not so sure i am willing to trust Obama either.