Usage patterns
〈物〉がわいせつだfor something to be obscene/indecent
This footage was judged to be obscene.
わいせつな〈物〉obscene/indecent (thing)
Obscene photos were circulating on the internet.
わいせつ行為an indecent act
He was arrested on suspicion of an indecent act.
わいせつ物を頒布するto distribute obscene material (legal phrasing)
He was fined for distributing obscene material.