I would think that I would inform my child well of the legal system and what is and is not illegal that they can do on the Internet. Teach, not dictate. No one loves a dictator. Now if I ever felt that they didn't grasp it I would confront them about it to absolve my fears.
I hope you at least told them about it before implementing it.
If my fifteen year old son decides he wants to veiw hot naked teens, and he's found out by law enforcement. Big trouble.
Teenagers are underage, and therefore, even though he himself is a teen, he, my husband, or myself can be labeled, at the discretion of the judicial system, a sixual predator. I ain't down with that.
You know, in the modern world, he is more likely to get such pictures sent via MMS than on his computer. On a computer he is vastly more likely to see older women.