Natural law
Natural law is a polysemic concept - i.e., there are several theories of natural law.
In English, one can distinguish natural law (lex naturalis) from natural justice (ius naturalis). Thomas Hobbes makes this distinction, and regards natural law as the law of the jungle and that natural justice arises out of natural law as consequence of a social contract. However not all natural law theorists are social contractarian. Aristotle likewise distinguishes between natural justice (dike, ius) and positive law (nomos, lex). For Aristotle some laws are positive, others are natural. Note that for Aristotle and antiquity, because natural law was universal in time and space it was also identical to international law.
Aquinas speaks also of a form of natural law as God's own law, i.e. divine law (Gottesrecht) as distinct from natural human law.
Late modernity focusses its attention on positive law. Many positivists regard equate natural law with divine law and reject it, or they reject natural law theory due to the naturalistic fallacy, i.e. confusing what is and what ought be. David Hume is often misread in this conjunction as having believed ought and is bore no connection, that one could not derive an ought statement from an is statement - which is not what Hume stated.
However, not all positivists regard natural law and positive law theories as contradictory. Some positivists simply do not concerns themselves with the issue of legal normativity.
The better view is to see some laws as universal in time and place, that is as natural (inevitable), and others as local and conventional (variable).
