So then China could, at any point, call up the US president and say "Look there's a drone in the room with you right now. Shut down all your nuclear facilities or I hereby declare war and you're dead within 10 seconds." Then failing that they could hit the VP next, Secretary of state, etc etc.
Point being the idea of sticking with WW2 "rules" with current and future technology is laughably implausible.
And I guarantee you the citizens of Israel would NOT think it's perfectly legit, legal, and fair if Netenyahu got assassinated with a drone along with his military commanders.