I agree that the U.S. military would have the legal authority to use predator drones on U.S. soil (even against American citizens) under some circumstances (foreign military invasion, civil war, etc.) But the U.S. military (excluding the Coast Guard and National Guard) is not allowed to operate in a law enforcement capacity on U.S. soil and so would not be tracking any enemy combatant (terrorist or otherwise) on U.S. soil. So the inclusion of "home" in your statement of "home or abroad" is pointless as long as we are limiting the use of drones to the military.
The question, as I see it, is not whether or not the military can use predator drones to kill American's on U.S. soil, but whether the U.S. government can kill anyone (citizen or not) who does not actively pose a threat without due process. Since the Coast Guard, National Guard, FBI, Department of Homeland Security, ATF, and I'm sure several other agencies do have "military" capabilities and could (if they don't already) have access to drones, the question remains. Could these agencies (with drones or by other means) legally kill someone who does not pose an imminent threat without due process? The question of drone use on American soil against Americans is a narrow focus of this larger question, but it's one that should be answered by our government (the Attorney General and the President in particular). The reason this question should be answered is that our government has stretched the concept of "imminent threat" to an absurd level (IMO) such that it has no real meaning. According to the Obama administration:
"the condition that an operational leader present an "imminent" threat of violent attack against the United States does not require the United States to have clear evidence that a specific attack on U.S. persons will take place in the immediate future."
So, they have already stated that they don't have to have any evidence that anything will happen now or in the immediate future. They just have to suspect that it will and that is justification for the military to use a drone to kill someone. It's not a stretch to believe that this same logic would be used by a domestic law enforcement agency as a justification to kill someone here without due process considering the concept of "imminent threat" now means that the government simply suspects that you might attack at some time in the future.
In my untrained legal opinion, it would be illegal for the U.S. government (excluding the military) to kill any person who does not actively pose a threat (whether or not they were an American and whether or not they were on American soil). Also, the idea that "imminent threat" does not require clear evidence that a specific attack will take place in the immediate future is asinine. So, while I agree that the question of military use of armed drones on American soil is generally pointless, the question of armed drones being used on American soil in a law enforcement capacity is valid and may very soon not be simply a hypothetical question.