Two Treatises on Government (1680-1690)
§ 197. As conquest may be called a foreign usurpation, so usurpation is a kind of domestic conquest, with this difference – that an usurper can never have right on his side, it being no usurpation but where one is got into the possession of what another has right to. This, so far as it is usurpation, is a change only of persons, but not of the forms and rules of the government; for if the usurper extend his power beyond what, of right, belonged to the lawful princes or governors of the commonwealth, it is tyranny added to usurpation.
§ 198. In all lawful governments the designation of the persons who are to bear rule being as natural and necessary a part as the form of the government itself, and that which had its establishment originally from the people – the anarchy being much alike, to have no form of government at all, or to agree that it shall be monarchical, yet appoint no way to design the person that shall have the power and be the monarch – all commonwealths, therefore, with the form of government established, have rules also of appointing and conveying the right to those who are to have any share in the public authority; and whoever gets into the exercise of any part of the power by other ways than what the laws of the community have prescribed hath no right to be obeyed, though the form of the commonwealth be still preserved, since he is not the person the laws have appointed, and, consequently, not the person the people have consented to. Nor can such an usurper, or any deriving from him, ever have a title till the people are both at liberty to consent, and have actually consented, to allow and confirm in him the power he hath till then usurped.