You could always ban advertising of it while making it legal, you know. It isn't as though children will be buying or viewing the stuff anyway, and it's not like you can stop the teenagers.
I have devoted my teenage years to stopping other teenagers from stupidity with moderate success levels. I now how to stop teenagers, I have made it my passion. I have created lots of enemies doing this and pissed a lot of people off, but its the only thing that I have done where I feel good about it as an achievement. First off Gov't has to get on the side of the parents and not teenagers, that is non-negotiable.
That's insane. Look, I don't like pornography either, but there are certain things that you can't legislate against and expect any success. Legislating against it presumably just increases the whole forbidden fruits aspect of its appeal. And, as I wrote earlier, it isn't as though children (defining "child", wrongly, as pre-puberty) will be buying it anyway.