All laws must have a moral backing, that is, a moral law as their foundation. Contrary to those who say that "You can't legislate morality," I say, "If you don't legislate morality, what do you legislate?" Without that moral foundation, any legislation is simply argumentum ad baculum, or (paraphrased) in English, "persuasion from the barrel of a gun." You will do what we say simply because we want you to do it. The only obligation that you have is to the government and there is no one greater than us to whom we are accountable. And if you don't like it, lump it.
Without some higher authority morality is reduced to ice cream; you like vanilla, I like mocha almond fudge. Except we're talking about morality here, so it becomes, you prefer not taking other peoples' stuff, I like to help myself to any of your possessions that catch my eye. Who's to say who's right? In fact, without that objective, authoritative moral standard, even asking the question "who is right," is nonsensical. If there is no higher standard there is no right or wrong, just personal preference; your decision not to steal is no better than my decision to steal.
Some people who want to deny the necessity of an objective, authoritative (thus God-based) moral foundation argue that we get our morality through periods of trial and error, discovering what works.
But who's to say what works for any given society? Certainly, cutting the hearts out of living victims kidnapped from other local tribes by the thousands seemed to work quite well for the Aztec civilization. African slavery worked great for most of the world (including most of Africa) for hundreds of years. Purging their society of the aged, the handicapped, and the Jews looked like it might "work" for the purposes of the Nazis. Without a moral standard outside of human government and culture, these atrocities cannot be judged as "wrong." Without an authoritative moral standard, the strongest statement one can make about these events is, "Personally, I don't like that." Seems pretty weak to me.
"But," the secularist argues, "all those examples involve hurting other people. Thus, we can say such actions are immoral." Really? Where does one, outside of an objective, authoritative moral standard, have the ability to say that hurting people is wrong? Let me put it another way: You claim there are no transcendent moral standards, but we shouldn't hurt people. If that's true, then isn't "not hurting people" a transcendent moral law? To say that there is not an authoritative Law Giver who we are obligated to obey, but at the same time claim that we are obligated not to hurt people is a contradiction. May I also point out that if we agree that "not hurting people" IS a transcendent moral law, then couldn't there be other transcendent moral laws as well?
The strongest statement the secular legal scholar can make is, "I don't like being hurt, therefore I chose not to hurt other people." Wonderful! That's an excellent reason for you not to hurt people, not for anybody else not to hurt people. What if I like hurting people? By what authority, other than one's personal preferences, could I then be told to change my behavior? There is none.
Without a God, who is The Moral Authority, people have no obligation to help or be concerned for others, all societies from the most violent and degraded to the most kind and altruistic are on the same level, one can't be said to be better than the other (the idea of "better" implies an objective standard). Words like "corruption" and "justice" become meaningless. There can never be such a thing as a moral reformer, such as Martin Luther King, Jr.; in fact, in what 99.8% of people would surely consider a bizarre twist, in a world where culture, society, or government truly was the highest authority, M. L. King, Jr. would be considered immoral (I'm not going to take up more space here demonstrating why that would be).
Without God, the whole philosophical basis for a justice system or a legal system breaks down completely. And the result are truly ugly to behold.
