unlawful vs improper

unlawful and improper both are adjectives.

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

As adjectives, unlawful and improper are synonyms defined as:

unlawful and improper: not conforming to legality, moral law, or social convention

Other synonyms of unlawful include unconventional.

unlawful (adjective)	improper (adjective)
contrary to or prohibited by or defiant of law	not suitable or right or appropriate
contrary to or forbidden by law	not appropriate for a purpose or occasion
having no legally established claim	not conforming to legality, moral law, or social convention
not morally right or permissible
not conforming to legality, moral law, or social convention