> Most things that are legal aren't outlined in the law anyway, they're omitted.
So for slavery, you would expect the laws to eg deal with run-away slaves etc, not so much with slavery itself.
> I think it is reasonable to conclude they were referring to the bulk of the law that is administrative/procedural/etc. There are 53 titles of US code, and one of those (title 18) is about criminal code. The rest are predominately not matters of morality.
Yes, exactly. And I am presuming here, that there is a presumption in morality that all-else-being equal, it's more moral to stick to these neutral laws, just because it makes living in a society with other people more bearable.
Eg in a moral sense it doesn't matter whether people drive on the left side of the road or the right side. But if there's a law about driving on the books, you better follow it.
(No clue whether this is strictly speaking something about morals or more about ethics?)