Yes, it's not as if child porn, or underage erotic pics, is something crystal clearly defined when it's handled legally. Pictures of somebody's children on the beach are a prime example. Or what about drawings? Even drawn sketches of kids that look like they could be of school age, maybe ten to twelve years olf, but which aren't realistic and not high on anything obviously sexual, can get filed as kid porn.

And public perception has grown harder over time, at least in the mainstream. No major record company today would want to touch this cover art, though it presented no problems in the mid-seventies.

http://www.discogs.com/viewimages?release=800548

http://www.peterice.com/YesLP_Yesterdays.jpg

(The bluish, languid figure on the front cover is clearly an underage girl, resting with her belly upwards; the black butterfly is near the point where her modesty would be. The boys on the rear cover are pretty incriminating by today's standards for commercial artwork too)