Topping terrorists, on whose authority?
The ethical question over the morality of killing terrorists seems to be the same as that raised in killing tyrants. Traditional Catholic teaching is to be found in the writings of the great medieval theologian St Thomas Aquinas. He considered it legitimate to kill a usurper, but only under a mandate from a legitimate authority. Murder requires an express mandate before a private person can lawfully kill even a tyrant. ..The Protestant view is more utilitarian.
In the Reformation period, most of the leading Protestants were surprisingly strongly in favour of killing tyrants. The Scottish reformer, John Knox, affirmed that it was the duty of “the nobility, judges, rulers and people of England” to condemn Mary Queen of Scots to death. One leading German reformer, the “mild Melanchthon”, argued that the killing of a tyrant is the most agreeable offering a man can make to God.
The right to free yourself, do you need permission from "authority" to do so or not? That is the crux of the question, and the clue as to history of subjugation.
As to the right to free yourself from the tyranny of terrorism, whose authority should we ask for permission? I think the Torah probably has a pragmatic answer to that as well.