That's trivial.
Not even when they think they know what God thinks.
That's true. But what's your point? That the gov't "shouldn't impose its morality on others"?
Well, what about laws regarding murder? Adultery? Theft? Zoning? Embezzling? Pornography? Public health? Should the gov't take a hands-off policy regarding these things?
Yes, we have the God-given freedom to choose good or evil, but at the same time, the government has the God-given responsibility to protect the lives of its citizens and to promote the common good.
Murder, adultery, theft, and embezzling violate the rights of others; drug use and pornography do not, and so are not the legitimate concern of government. (Zoning and public health laws are gray areas in that they can protect individual rights but those powers can also be abused.)