unlawful vs illegitimate

unlawful is not a noun while illegitimate is a noun.

Word	Noun	Adjective	Verb	Adverb
unlawful	No	Yes	No	No
illegitimate	Yes	Yes	No	No

As adjectives, unlawful and illegitimate are synonyms defined as:

Other synonyms of unlawful include illicit, outlaw, outlawed.

unlawful (noun)	illegitimate (noun)
	the illegitimate offspring of unmarried parents

unlawful (adjective)	illegitimate (adjective)
contrary to or prohibited by or defiant of law	of marriages and offspring; not recognized as lawful
contrary to or forbidden by law	contrary to or forbidden by law
having no legally established claim
not morally right or permissible
not conforming to legality, moral law, or social convention