Uhh... what?
You must be excluding the ACTUAL child porn that's sold in Akiba. I can point out three shops that sell porn -WITH- children, and I'm not talking about women who look young and that are running around in a swimsuit either, I mean full-on penetration and even advertising as 11, 12 and 13 year olds.
It's fine to say "well the idol stuff will have more regulation" but when it comes to it, I'm quite sure this law is mainly aimed at the real child porn out there, as North Americans might know it.