I somewhat addressed this objection in my previous post, but I had a further thought on this. The objection in question is “Without the Law of God, we have no guide or basis for what the government would outlaw.”
I sincerely disagree. It forgets the purpose of criminal justice. The supporters of Theonomy would charge that the purpose of criminal law is to uphold a standard of right and wrong for the sake of that standard. This is wrong. The purpose of criminal law is to provide justice for those who have been victimized.
How do we know if we should outlaw X if we don’t have the Law of God to tell us so? Simple. Is there a victim? If there’s a victim, then there is someone who needs the government to carry out justice for them.