As many others have pointed out, "engaged in combat" has the potential to be interpreted in dangerous ways.

I think the drone issue is distracting people from what I feel is the more important issue: Our government has taken the official position that it can legally assassinate its citizens. So they can't legally kill me with a drone... small comfort if they can just assassinate me in some other fashion.

(yes, I know that government agencies have assassinated American citizens [not to mention non-citizens] in the past, but making it official doctrine is quite an escalation)