As the Boss said in
Cool Hand Luke: "What we have here is failure to communicate."
I may be responsible for that, so I'll try to remedy it.
I'm not sure just what Natural Law is, myself. If it exists, however, I think laws adopted by human governments are not the same as Natural Law. They exist apart from it, and regardless of it.
That's not to say that beliefs regarding what Natural Law is and says do not play a part in the adoption of certain of our laws, or that they do not influence, sometimes, the interpretation and enforcement of our laws. We may say the same of beliefs about what God wants of us, which may be the same thing as Natural Law, or other views regarding what is or is not moral. Such beliefs also may lead us to claim that certain laws are bad laws.
Legal positivism/realism doesn't maintain that every law is good. It merely maintains that every law is a law. It doesn't cease to exist if it's bad.
But our laws, once adopted, are not a part of Natural Law or the will of God. They become part of a vast system of rules and regulations meant to apply to all kinds of human conduct and interaction, most of which, I know from having to look up and research the damn things all the time, have little or nothing to do with God or Natural Law. The fact that most laws have nothing to do with what's right or wrong in a moral sense itself makes the claim that law is Natural Law or are divine commandments seem foolish, to me. As does the fact that laws which are adopted because they are thought to be good or moral are often more destructive in their practical application. The classic example here is Prohibition--a constitutional amendment, sad to say.
So, when people say that Natural Law is the real or true law, and that the laws we humans adopt aren't really laws unless they conform to Natural Law, I maintain they confuse Natural Law, the contents of which may in any case vary over time and place and are not acknowledged as effective, binding and enforceable in a legal system, with what actually is the law we adopt. Likewise when they claim that we have rights by nature or by the Will of God which have not been recognized as part of a functioning legal system and therefore cannot be enforced if they violate and conflict with other rules adopted in that system, they confuse what they think should be the law with the law is at the time.
What the law is is not what we think it should be, or we think Nature or God requires it to be. If we think a law is bad, we think it should be changed or revoked, not that it doesn't exist.
That's all, folks.