One of the most radical French expressions of the right of resistance was that voiced by Phillipe du Plessis-Mornay in his Vindiciae contra tyrannos (1579) (commonly know in English as A Defense of Liberty Against Tyrants [this rare book is available on SWRB's Puritan Hard Drive] - ed.). Julian H. Franklin has said that Mornay was not a theologian trying to soothe conscientious doubts, "but a soldier and a statesman exhorting to revolt." Still, Franklin himself is willing to admit that Mornay is more militant than Beza when it comes to considering the issue of resistance on religious as opposed to strictly political grounds.
If the vassal does not keep the fealty he swore, his fief is forfeited and he is legally deprived of all prerogatives. So also with the king. If he neglects God, if he goes over to His enemies and is guilty of felony towards God, his kingdom is forfeited of right and is often lost in fact.
Mornay extends this obligation to all nations, regardless of their constitutional history, basing his argument on what is commonly referred to as "covenant theology": The people and the king enter a covenant with God to maintain proper order, including, of course, proper order in worship. Each individual, as well as the king, is responsible for seeing that his covenant is fulfilled.
The importance of the worship issue for Mornay's covenant theory becomes apparent when he tries to provide a historical example.
Mornay uses the case of King Josiah, indicating that the covenant between God and the Jews stipulated that "the king and his entire people would worship God according to the prescription of His Law (i.e. the regulative principle of worship—ed.) as individuals and would act collectively to protect their worship."
Moreover, Mornay is not content with merely using this ancient covenant as an example. He insists that the same principles apply to his own day, arguing that Christian rulers stand in the place of the Jewish kings, and that it is their duty to ensure the fulfillment of God's Law.
Mornay proposes that if the ancient Jews were enjoined to resist godless rulers, the same must surely hold for Christians. Mornay stipulates that it is the duty of the people to safeguard pure worship. When dealing with this issue, then, Mornay insists that the question of idolatry is of prime importance, particularly because the violation of "pure worship" and the persecution of the true Church are the principal grounds for resistance...