Zarlak
my face causes global warming
I'm not up to speed with U.S. criminal law but it seems to me that a person committing murder doesn't necessarily has to 'use his own hands' so to speak.
If we consider this simplified scenario: Obama gives orders to random military person in the desert to kill a civilian (and other people supposedly, 'targets') in the Middle East. Obama didn't actually 'pull the trigger', but used the military person as a simple tool it could be him that is the principal.
I'm now quoting a random book google books showed me (and I know it's English Law but I assume them to be similar, happy to stand corrected though) page 184 first sentence: "An exception to the aforementioned rule that the pricnipal must directly bring about the actus reus can be seen in the doctrine of innocent agency. This notion can best be compared to the doctrine of perpetration by means. If the person who actually committed the actus reus cannot be regarded as a participant (edit: in this case the military person) in the offence, because he acted without the necessary means rea; the master behind the scene who pulls the strings is regarded as the perpetrator. [...]"
So it seems that he actually can commit murder by ordering drone strikes, if we allege he was involved in one actual case not a general order like "using drone is legit".
What you could bring on your side is that it still needn't be murder if the casualty of a civilian is justified by some greater good aspect like it also killed Osama B who was about to blow up a market. That's very well plausible but it's a pretty big stretch still for criminal law because the actual danger coming from that person would have to be imminent and I'm not too convinced 'imminent' in the legal sense can be fulfilled from an intelligence point of view.
Murder has to be unlawful. If the law allows him to do it, then it isn't murder. Murder does not mean 'to kill another person or be responsible for a persons death'. It's a specific word invented to fit a specific circumstance.