That the aggressor, who puts himself into the state of war with another, and unjustly invades another man’s right, can, by such an unjust war, never come to have a right over the conquered, will be easily agreed by all men, who will not think, that robbers and pyrates have a right of empire over whomsoever they have force enough to master; or that men are bound by promises, which unlawful force extorts from them. Should a robber break into my house, and with a dagger at my throat make me seal deeds to convey my estate to him, would this give him any title? Just such a title, by his sword, has an unjust conqueror, who forces me into submission. The injury and the crime is equal, whether committed by the wearer of a crown, or some petty villain. The title of the offender, and the number of his followers, make no difference in the offence, unless it be to aggravate it. The only difference is, great robbers punish little ones, to keep them in their obedience; but the great ones are rewarded with laurels and triumphs, because they are too big for the weak hands of justice in this world, and have the power in their own possession, which should punish offenders. What is my remedy against a robber, that so broke into my house? Appeal to the law for justice. But perhaps justice is denied, or I am crippled and cannot stir, robbed and have not the means to do it. If God has taken away all means of seeking remedy, there is nothing left but patience. But my son, when able, may seek the relief of the law, which I am denied: he or his son may renew his appeal, till he recover his right. But the conquered, or their children, have no court, no arbitrator on earth to appeal to. Then they may appeal, as Jephtha did, and repeat their appeal till they have recovered the native right of their ancestors, which was, to have such a legislative over them, as the majority should approve, and freely acquiesce in. If it be objected, This would cause endless trouble; I answer, no more than justice does, where she lies open to all that appeal to her. He that troubles his neighbour without a cause, is punished for it by the justice of the court he appeals to: and he that appeals to heaven must be sure he has right on his side; and a right too that is worth the trouble and cost of the appeal, as he will answer at a tribunal that cannot be deceived, and will be sure to retribute to every one according to the mischiefs he hath created to his fellow subjects; that is, any part of mankind: from whence it is plain, that he that conquers in an unjust war can thereby have no title to the subjection and obedience of t he conquered.
John Locke, Two Treatises of Government, London, 1690, second treatise, sect. 176