The Religious origins of Law

I want for those Christians who say that we do not need to follow God's law any longer, but emphasize that we do need to follow man's law, to carefully consider the following:

"Law is in every culture religious in origin. Because law governs man and society, because it establishes and declares the meaning of justice and righteousness, law is inescapably religious, in that it establishes in practical fashion the ultimate concerns of a culture. Accordingly, a fundamental and necessary premise in any and every study of law must be, first, a recognition of this religious nature of law." RJ Rushdoony, Vol. 1, The Institutes of Biblical Law, p. 4

Also:

"Modern humanism, the religion of the state, locates law in the state and thus makes the state, or the people as they find expression in the state, the god of the system." Ibid. p. 5

I am truly saddened to have realized while typing this paragraph that many Christians today, Christians who will say on the one hand that we are no longer required to follow God's perfect law, will, when confronted with something completely biblical yet illegal according to humanisms current, rather fluid law systems (such as homeschooling in the recent past, or perhaps plural marriage in the future), run off and grab their bibles, ruffle through the pages, and find the verses from Paul (Romans 13:1-7) that tells us that we must obey the law of the land! Have they forgotten Daniel? What about Acts 5:27-29? Whom is it that they really serve, God or man?

Grace & Peace,
Joshuah