Please show me the constitutional mandate that allows US citizens to be assassinated because they are on foreign soil, but would not allow it on domestic soil.
Please show me the constitutional requirement that military forces of the United States must inquire into the citizenship status of an active enemy of the Unites States before engaging him with deadly force.
Does it make sense to you that any active enemy who holds US citizenship and manages to make it to an area of the world where they cannot be reached using traditional law enforcement means should be untouchable?