One difference between a theonomist and a Reformed Libertarian is that the former argue that the Bible offers a political system, a set of laws for government to enforce. For the theonomist, this was originally provided of course in the Old Testament– the Mosaic law. And since, according to their view, these laws were never specifically abrogated, they are to be understood as still in effect. Thus, the Bible demands a certain system and governments are bound to uphold this law.
Some conflate a similar framework with what has come to be known as Reformed Libertarianism– that is, certain well intentioned folks wrongly agree with the theonomists that the Bible has given us a set of laws for government to enforce: it’s just that they are more libertarian ones!
This is a misleading way to look at the problem. It is better to sharply differentiate between a positive law (civil rules of a particular community to be enforced by a government/magistrate) and a moral law. A moral law is synonymous with “Natural Law.” Natural law refers to a law that transcends particular human contexts– it has to do with Ethics, which is not bound by time and space and people group.
Under this framework, the Mosaic civil laws were not abrogated in the sense that certain ethical principles were abrogated. Rather, they were abrogated to the extent that the “particular community,” which existed under a specific covenant no longer exists. It no longer exists because it was always meant to be temporary and to point forward to a better community (the church) under a better covenant (the New Covenant). The Mosaic law code was positive law. It was an application of moral law for the Israelite situation.
Thus, for the Reformed Libertarian, we don’t claim that the Bible offers a specific political system or set of laws for government to enforce. We approach the problem from a different angle altogether; namely, we observe that Natural Law (Ethics) does not have exceptions in regards to the individuals to whom it applies. Since every person is held to the same ethical standard, the implications extend to questions of which types of actions are legitimate for those in a position of governance.
In other words, we don’t go looking in the Bible for a blueprint for building the perfect government system. We merely have a set of ethical principles that we hold each person to indiscriminately. And since the government is made up of persons, we extend the logic to them.
Why are we comfortable with the idea that God doesn’t have a revealed set of positive laws for governments today? Simple: because the New Covenant era is about the spiritual kingdom; eternal things.
By conflating moral law with positive law, all sorts of difficulty is unavoidable.