Ultimately, I think the basis of law can be summed up in a single sentence: "Sin is cruelty and injustice; all else is peccadillo." (Star, in Glory Road by Robert A. Heinlein) [This is somewhat ironic, as "peccadillo" means "little sin".]
IMHO, human law should ban:
- harming other people, deliberately or through carelessness
- harming the property of other people
- taking or using the property of other people without their consent (stealing, robbery)
- lying to other people to get their property (fraud) or to a third party to get the third party to take away their property for you (perjury/false witness)
This can still cover a lot of ground. Pollution harms other people and makes their property dirty. False advertising is a form of fraud.
But laws about what people consentingly put in their own bodies (the "war on drugs"), what they do with other consenting people in bed ("sodomy"), etc. are simply attempts to enshrine the divine law in human law.
This is a mistake, especially in a pluralistic society like the US(*). God will enforce his own law: he doesn't need our help. If God disapproves of (for example) "sodomy"(+), He will punish it in his own way. Legislating against it is like writing laws requiring that objects fall at 1/2gt^2 when not supported in some way.
(*) Even if you ignore the small minorities of Buddhists, Hinduists, Baha'i, etc., and the large minority of atheists, the fact remains that the US has large populations of Roman Catholics, "mainstream" Protestants (Lutheran, Methodist, Episcopalean, etc.), Evangelical Protestants (Southern Baptist, Pentacostal, etc.), Jews and Muslims. These various branches of monotheism have very different ideas of what God demands of us.
(+) As late as the mid-20th-century, most states Sodomy laws simply banned "the act against nature" without further defining it. All the canids use it to express dominance/submission, Black Swans, Penguins, some Dolphins, various apes, Elephants, lions, dragonflies, fruit flies, even bedbugs practice it in some form. Calling this "unnatural" or "against nature" is just plain silly.
Source: Wikipedia: http://en.wikipedia.org/wiki/Homosexual_behavior_in_animals