ethical code vs system of rules

ethical code and system of rules both are nouns.

Word	Noun	Adjective	Verb	Adverb
ethical code	Yes	No	No	No
system of rules	Yes	No	No	No

As nouns, system of rules is a hypernym of ethical code; that is, system of rules is a word with a broader meaning than ethical code:

ethical code: a system of principles governing morality and acceptable conduct
system of rules: a complex of methods or rules governing behavior

Other hypernyms of ethical code include system.

ethical code (noun)	system of rules (noun)
a system of principles governing morality and acceptable conduct	a complex of methods or rules governing behavior