Originally Posted by R. Scott Clark

If the 16th- and 17th-century Reformed were correct, the decalogue is a reflection of the natural law (a corollary to the republication doctrine). We don't need to appeal to Mosaic case/civil law to argue for civil enforcement of the second table.

The family is the basic, creational, natural, social unit. Adultery is a crime against nature. It violates the social contract implicit in the marriage vows (whether taken in church or before the magistrate). It weakens and essential relation and destabilizes a community. It is also a form of theft.

A marriage is a civil, not just religious, covenant. Transgression of the marriage covenant is a transgression of a civil covenant. Every transgression of the civil covenant, e.g. the reckless use of an auto or firearm is punishable by the magistrate.

We don't want the magistrate punishing sins of the heart but we dot want him punishing crimes against nature and the civil contract implicit in nature and social relations. That's why he bears the sword.