Hypothetical: A guy is about to publish a leaked document that will expose dozens of our undercover agents, currently working undercover in dangerous places, ensuring their almost certain torture and death. The guy is a foreign national. Are we justified in killing him as an enemy combatant?
I say yes.
If you can murder him, why not arrest him? Make the people believe that legal justice is still what we do in America. Calling for the murder of "enemies of the state", "terrorists", & "spies" really opens Pandora's Box. The Judicial Branch needs to keep its seat at the table.