Though I believe VanDrunen’s epistemology and understanding of natural law have significant problems, I believe his covenantal perspective as it relates to political philosophy is basically correct. At the end of Divine Covenants and Moral Order, he tries to apply his general framework to more practical conclusions, including the question of religious liberty.
[C]ivil government [is] the natural institution most prone to usurp authority and to exercise raw power… The promotion of justice… is the very basis for civil government’s legitimacy. Thus its authority is inherently limited by the obligation to do what is just. Any injustice is usurpation… [J]ustice grounded in the natural law should be proportionate, retributive, restorative, and forbearing (and therefore flexible in application)…
To defend this claim [of religious liberty] I turn again to Genesis 9:6: “Whoever sheds the blood of man, by man shall his blood be shed, for God made man in his image.” Of the many significant things about this verse, perhaps most profound is the fact that God, the supreme governor and judge of the world, has delegated aspects of the administration of justice to human beings… Though dispensing retributive justice against fellow humans would have been unnecessary in an unfallen world, in a fallen world imposing just punishment upon wrongdoers becomes a necessary aspect of human rule. To rule a sinful world means, in part, ensuring that those who injure another human person receive appropriate and proportionate retribution.
What God delegates to human beings here is the administration of intrahuman justice. To put it another way, God ordains that human beings should impose punishments for injuries inflicted upon each other. God does not delegate authority to impose just punishment upon wrongs that a human being commits against God himself. From one perspective, of course, any injury inflicted upon a human being is a wrong against God whose image that person bears, so I will modify my claim in this way: God delegates to human beings the authority to impose punishments for wrongs insofar as they are injuries inflicted upon each other, but not for wrongs insofar as they are inflicted upon God.
Thus to return to the question at hand: Does the Noahic covenant shed any light on whether human society might prohibit or penalize the worship or instruction of a particular religion? Yes, and it indicates that human beings do not have such authority. According to the Noahic covenant, human beings have the authority to use force against one another in order to impose proportionate penalties for intrahuman wrongs. For intrahuman crimes such as murder or theft, there are concrete and definable injuries, and just legislators and judges can design penalties that match their severity. But acts of improper religious worship are offenses against God. In such cases human beings are inherently incapable of imposing a proportionate penalty. What sort of human punishment is proportionate to a wrong done against an infinite and eternal God? Even if one were to claim that a teacher of false religion is corrupting the religious sensibilities of the youth, for example, and thus is guilty of an intrahuman injury, it is difficult to perceive how any human court could objectively determine the character and extent of this injury so as to impose a proportionate penalty.
First, VanDrunen’s distinction between crimes against man and crimes against God (which he applies to the Mosaic Covenant) is precisely how I have explained lex talionis’ function in the Mosaic Covenant.
Second, VanDrunen is correct that religious persecution is a violation of lex talionis and is not an administration of retributive justice. Therefore no one may use force against anyone else for practicing a (non-violent) false religion. To do so is usurpation. This is the only non-contradictory way to argue for religious liberty. Every other attempt to justify religious liberty undermines itself by inconsistencies.
Third, if humans may only use force against other humans to administer retributive justice for physical harm done to humans (that is – if “public utility” is no justification for the use of force), then the vast, vast, vast, vast majority of what the United States and other nations currently do is usurpation not backed by any God-given authority.
In other words, the non-aggression principle is biblical and it is the only consistent defense of religious liberty.