Yes, it is too abstract a concept to apply in real situations. However, we can view it as "freedoms" rather than rights which humans possessed in a state of nature before government existed. They had absolute freedom of speech, religion, drug use, etc. This argument says humans chose to give up some of their freedoms in order to have a government that protected their lives and property.
A more realistic view is probably that they were subjected to the government that conquered their tribe.
OK I'll sign on that there was in cave man days a then an existing state of nature with various attributes. I'll agree that rule of law, religious rules, customs and morays and traditions have augmented them.
I simply have seen religious and poltiically active people before online claiming this thing called "natural law" as a tool to claim to this or that behavioror prohibition of behavior as a right they enjoy when it contravenes Scotus opinions
on constitutional law. But pecking apart the construct of natural law it is masking a deity but performing its function as some meta law concept, yet it comes down to a person simply asserting an arbitrary behavior they want or don't want
is correct, without anything in reality to elevate it or support it.
You could say we all have a natural law right to be free. I could assert a natural law right to slaughter each first born son who was born on a wednesday of all farmers.
In the final analysis the only difference is that most people agree with you and not with me, not that you are provably right by reference to this invisible and indescribably
whatever that nobody has sufficiently identified.
Fair play, substantial justice, peace, prosperity, life, egality, truth.... these are bedrock as much as we can get by reason to broad inductive concepts. I don't see what "natural law" adds at all.
It' a religious persons end run to skirt the law, IMO