How about just let parents take basic precautions when they let their kids access the Internet like setting up a firewall. It's a parents responsibility to manage what content their kids see, not the government. If they want to help parents then do some self labeling regulations so the content is easier to block instead.

Here's your new regulation: all porn sites must add an ageRating="18" meta tag to the html header. Done, now you have an easy way to set up a browser to block porn.