https://en.wikipedia.org/wiki/Natural_lawIt's an orthogonal concept to human rights btw, there's human rights laws, and treaties, both of which are positive law. Similarly, there's laws proper about almost every non human-rights subject (say investment vehicles), and there's natural law about every other subject (say investment vehicles).
Another concept I would recommend looking into are courts and legal process. Otherwise, I'm not sure what you think happens when your belief of what natural law is, clashes with someone else's vision. The body of procedural law tends much more towards positive law out of necessity, otherwise it would devolve into recursive disagreements as to what the process (and the process for handling process disputes(and the process..)) is, a disregard for natural law and respect for the positive law as a sort of convention arises out of practicality at least in the process, arguably leaking into actual substantive law.
Jurisdiction might be a good next step to tie it into this thread's topic, what happens when there's a dispute as to whose rules and courts should judge a matter? The importance of positive law in this matter is mostly accorded by courts unanimously, and the borders of countries are written in constitution in blood. We tend to err towards not rewriting those as they are 'expensive'.