Are we to assume everyone on the planet, even enemy nationals, are protected by the constitution?
That certainly makes war a tough row to hoe.
Not really: simply kill the enemy.
Are we to assume everyone on the planet, even enemy nationals, are protected by the constitution?
The Constitution sets limits on what the government does, otherwise it is useless.
Moreover, the government can [and does] claim that certain actions may result in a loss of citizenship; if that is the case, and if the Constitution only protects citizens, then your protection by the constitution as a citizen is entirely at the whim of the government.