You always say that natural law applies to beings with capacity to understand it. i disagree..
Natural law applies to you whether you understand it or not, whether you have the potential to understand it or not.
If you are a sentient being living and interacting with other sentient beings, if you think and/or act immorally, you will live chaotic lives.
the main difference is scale, when we think and act immoral on a societal scale we destroy everything around us as well.

But to say once you reach a certain level of intelligence (or rather capacity to have a certain amount of intelligence) suddenly natural law applies to you just sounds mumbojumbo, cause it isn't true.
It applies no matter what.
Animals may act more on instinct, but they too have free will.