"For where the injured Party may be relieved, and his damages repaired by Appeal to the Law, there can be no pretence for Force, which is only to be used, where a Man is intercepted from appealing to the Law. For nothing is to be accounted Hostile Force, but where it leaves not the remedy of such an Appeal. And 'tis such Force alone, that puts him that uses it into a state of War, and makes it lawful to resist him. A Man with a Sword in his Hand demands my Purse in the High-way, when perhaps I have not 12 d. in my Pocket; This Man I may lawfully kill. To another I deliver 100 l. to hold only whilst I alight, which he refuses to restore me, when I am got up again, but draws his Sword to defend the possession of it by force, if I endeavour to retake it. The mischief this Man does me, is a hundred, or possibly a thousand times more, than the other perhaps intended me, (whom I killed before he really did me any) and yet I might lawfully kill the one, and cannot so much as hurt the other lawfully. The Reason whereof is plain; because the one using force, which threatned my Life, I could not have time to appeal to the Law to secure it: And when it was gone, 'twas too late to appeal. The Law could not restore Life to my dead Carcass: The Loss was irreparable; which to prevent, the Law of Nature gave me a Right to destroy him, who had put himself into a state of War with me, and threatned my destruction. But in the other case, my Life not being in danger, I may have the benefit of appealing to the Law, and have Reparation for my 100 l. that way."
-John Locke's "Two Treatises of Government: Right of Revolution"