Child pornography isn’t illegal because of the contents of the speech. It’s illegal because it’s an accessory to the original crime of child molestation. That is why the Supreme Court has consistently ruled that virtual child pornography, even photorealistic, is Constitutionally protected speech.
Okay but you're can surely realise that someone in possession of child pornography images that were taken, say, 20 years ago is no longer accessory to the original crime in any way. In fact, it might very well be possible for that person to not have even been born back then. Of course, that's not really how law works because some crimes don't have a deadline.
But whatever the legal reasoning behind it is, the consequence is that you are pretty much forbidden from distributing this material on the internet and so your right to show something to others is being restricted. I would consider that a limitation of free speech. But of course, I can totally see why you'd have the need to justify it in some other way, because we don't want our freedom of speech to be limited in any way. The law is always open to interpretation after all.
What's the reasoning behind restricting people from sharing copies of copyrighted material? Obviously it is also an illegal action. My point being, there are many ways in which our speech is monitored and restricted already.
