are you saying that assasination is legal, but you don't know if this one qualifies or are you asking if any assasination attempt is legal?
generally speaking gerald ford in 1976 made an executive order to forbid us agencies from assasinating world leaders. but that executive order can be set aside by any president under various reasons (preemptive strike, self-defense for example-- reagan used that rationale when bombing gaddafi)
killing "terrorists" by any means has been the U.S. policy since i can remember-- certainly nixon, ford, reagan, bush sr, clinton thought it was.
technically, we're not at war with any sovereign nation-- we're supporting military operations of sovereign nations (afghannistgan, iraq) to kill or capture their enemies.
the taliban are considered enemy combatants-- why would their leaders be any less a valid target than the jihadi peasant with a AK-47?
I am not asking if assassination is legal. Ford's executive order only covers world leaders, the second, or third, or forth in line would not be covered by Ford's order.
You don't think there is a fuzzy line, if not a clear line, between the popularly supported Taliban as a government entity, and al Qaeda, a jihadist / terrorist organization? If we can confligrate 'terrorist' into any popularly supported leadership role, what restrictions are placed on the label 'terrorism' or 'terrorist'?
For the moment, we do not know the combat situation around this airstrike. So, it could be that it was a combat situation: Us Guys Shooting at Them Guys and Them Guys Shooting as Us Guys.
But I do not believe that just because an Predator drops a laser guided bomb, that we are therefore in a combat situation. If we are going to start assassinating people with the United States Military, let's have a debate about it; let's us figure out what rules and ethics by which we are going to execute these tactics.
The fact is, the Taliban is experiencing a resurgence in Afghanistan. Are they all legitimate targets? If so, it seems to me we need to do a whole lot more killing over there. And we are going to be creating more enemies with each killing.
A correct analogy is the Hyrda, you cut off one head, and two more grow in its place. So, we, as a country, better be damn sure of the destination.