Lex, Rex, or The Law and the Prince; a Dispute for the Just Prerogative of King and People, published in 1644, is probably the greatest work on the foundation, nature and constitutional limits of Government, the Civil Magistrate, and the separate but mutual relationship of Church and State ever written. Lex, Rex is often taken to mean ‘the law is king’ i.e. the king is not above the law, but subject to it, which is certainly the substance of Rutherford’s thesis. Rutherford argued that “all civil power is immediately from God in its root”, and “power is a birthright of the people borrowed [by a ruler] from them”. The people may recover this power from a tyrant who abuses it by oppressing them. Rutherford wrote the book in response to a 1644 work by John Maxwell, formerly Bishop of Ross, entitled, The Sacred and Royal Prerogative of Christian Kings, which defended absolute monarchy and the divine right of kings. In Lex, Rex, Rutherford answers 44 questions about the duties of the civil government in governing a nation under God. It was the death knell of the divine right of kings dogma, and Charles I was said to have remarked that it could not be answered. So much so that it was burnt by the common hangman after the Restoration and it was punishable by death to own a copy of Lex, Rex.
John Macleod, in Scottish Theology, points out that “the tradition of Scottish Reformed teaching in regard to the obedience that the people owed to the civil power was to the effect that the power of the king is restricted and that his authority has bounds within which it ought to be kept. . . . Of this teaching, the best-known document that there had been so far was Buchanan’s De jure regni apud Scotos” (On the Right of Kingship among the Scots)”.
Perhaps the four key principles of the book are:
1) God gives no moral power to the King to commit immoral acts. 2) Kings can and must be justly held to their constitutional oaths, no less so than the people. 3) God stamps no person with the imprint of king, leaving such a designation to the people. 4) All kings owe their offices and powers to Christ. 5) Obedience to kings in unlawful acts is rebellion against Christ.
There is an outline of Lex, Rex here and an audio version of the book.
There is also a synopsis here.
There is a guide to it, written by David Field of Oak Hill College here. Field has a published chapter here, which is helpful in relation to resistance theory. Field also writes on Rutherford and the confessionally Christian State here and here. See also here.
There is a discussion of the relation between Lex, Rex and the American Founders in David W Hall’s book Genevan Reformation and the American Founding
The Lesser Magistrate and the Theology of Resistance Dr. L. Anthony Curto (mp3)
Ford, John D. ‘Lex, rex iusto posita : Samuel Rutherford on the origins of government’. In Mason, Roger A., Scots and Britons : Scottish political thought and the union of 1603 (Cambridge: Cambridge University Press, 1994), 262-90.