“199. As usurpation is the exercise of power which another hath a right to, so
tyranny is the exercise of power beyond right, which nobody can have a right to;
and this is making use of the power any one has in his hands, not for the good
of those who are under it, but for his own private, separate advantage. When the
governor, however entitled, makes not the law, but his will, the rule, and his
commands and actions are not directed to the preservation of the properties of
his people, but the satisfaction of his own ambition, revenge, covetousness, or
any other irregular passion.” http://classicliberal.tripod.com/locke/2treat11.html [Emphasis added]
In this manner John Locke began chapter 18 “Of Tyranny” of his Second Treatise on Civil Government. We must remember that he wrote this work during the 1680s in response to the Stuart Restoration of James II as king of England. Specifically, Locke sought to refute Sir Robert Filmer’s Patriarcha which argued in favor of absolute monarchy since kings are descended from Adam. He imagined monarchs to be like the fathers of their subjects.
Locke’s First Treatise on Civil Government examines and refutes Filmer’s work in great detail. In the Second Treatise Locke presents his own vision of civil government. A helpful overview of Locke’s thought is here http://plato.stanford.edu/entries/locke/#TwoTreGov
However, this summary does not emphasize Locke’s focus on the Bible as a key to his understanding of civil government.
Of course, any magistrate or judge may become a tyrant. As Locke wrote in Second Treatise, Chapter 18 sec. 202. “Wherever law ends, tyranny begins, if the law be transgressed to another’s harm; and whosoever in authority exceeds the power given him by the law, and makes use of the force he has under his command to compass that upon the subject which the law allows not, ceases in that to be a magistrate, and acting without authority may be opposed, as any other man who by force invades the right of
The law binds the ruler or political authority as much as (or even more than?) it binds the individual. This idea laid the foundation for the English Bill of Rights in 1689, the Declaration of Independence in 1776, and the American Bill of Rights added to the U.S. Constitution in 1789.