According to john yoo's letter, the government's duty to defend the united states from terrorists gives the federal government the right to

This is a very difficult argument.  Civilians must never be victims of war and the army must do all that it can to avoid inflicting casualties on civilians.  The difficulty here is that terrorists often hide within civilian surroundings and use civilians as shields.  What government needs is not only better technology but better intelligence. Still, as hard as it sounds, so long as civilians are in the line of fire, there will be victims.