Laws grounded on the Bible do not attempt to save man or to usher in a brave new world, a great society, world peace, a poverty-free world, or any other such idea. The purpose of Biblical law, and all law grounded on a Biblical faith, is to punish and restrain evil, and to protect life and property, to provide justice for all people. It is not the purpose of the state and its law to change or reform men: this is a spiritual matter and a task for religion. Man can be changed only by the grace of God through the ministry of the word…
Humanistic law has a different purpose. Humanistic law aims at saving men and remaking society. For humanism, salvation is an act of state. It is civil government which regenerates man and society and brings man into a paradise on earth…
Only when we return to a Biblical foundation for law shall we again have a return to justice and order under law. ‘Unless the Lord builds the house, they labour in vain that build it.’ 
When ungodly men in government try to remake society, look out society. They want to change everything around us. Denying original sin which they consider just a myth, they believe that man is basically good. So, nothing that they do could ever be evil, and every remembrance of Biblical Christianity in the community has to be removed because, after all, it’s just a hindrance, isn’t it? Then, its full steam ahead for change, and yes, “We can do it!”
This has been the attitude of the revolutionaries, ever since the French Revolution. It continues today (but in more camouflaged forms), in the socialist politics of the left. And it must be said that conservative parties are influenced by this too.
But laws cannot save man; they only affect us externally. Only God can ever save us, in the person and work of Jesus Christ. Not only can God save us, He has the only true prescription for the construction of a free society, based on His law. Every other form of law quickly shows itself to be abusive, or tyrannical.
Is Biblical law ever enough? No, for that would infer that salvation by law is possible. But even Biblical law cannot save us from our sins. Why should we expect man’s law to do so? Without the grace of God in a community, there is no salvation. That’s why God’s law AND His grace are the essential components of a free and healthy community.
This illustrates something else. In a godly society, there will be a healthy interaction between preachers of God’s Word, and the lawmakers. Why? Because they both get their marching orders from the one true God, in His book, the Bible. The Church and civil government are to be interdependent institutions, working in harmony with the other essential social institution, the family, to carry out God’s purpose.
So, there must be an awareness of roles, and a willingness to stay inside the God appointed spheres of life. These spheres are identified in the Bible for our understanding and benefit. In fact, the Bible gives us clear examples of how men have sometimes got themselves into hot water (or worse, been killed) when they failed to observe the God defined spheres of institutional responsibility.
Now, some would probably be saying, “Is it really as simple as that?” Well, it is. When Christians, the Church and the community at large begin to understand the Biblically defines spheres of responsibility, and the majority of the community is willing to submit to God, observing His will, the potential for the community (wherever it may be in the world), is remarkable.
And this is the outcome He wants us to work towards, for “blessed is the nation whose God is the Lord…” (Ps.33:12).
 Rousas Rushdoony, “Law and Liberty,” 1984, p.5-7.