Maybe a lawyer out there can answer that. Is there a law in the US code that allows law enforcement to intentionally kill innocent civlians in the course of stopping or aprehending a criminal?
If a gunman is shooting in a crowd, does that give the government the right to machine gun the entire crowd in order to kill the gunman?
What the government may try and rely on is a "act of war" angle. For years we have been skating closer and closer to defacto negation of the Posse Comitus (sp?)law.
It is immoral, IMHO, to authorize the shootdown of an airliner full of innocent people, when at the same time, the government intentionally denies the commander of the aircraft the basic tools to defend the command of that aircraft, and thereby possibly negate the perceived necessity destroy the aircraft and kill innocent passengers and crew.