I don't think we do. We have definitions of obscene material (though they are rather problematic). We have definitions of sexually explicit material. But I don't think we really have good legal definitions of pornography. For example, is
Eyes Wide Shut a pornographic film? It's sexually explicit, but I don't think most people would categorize it as pornography. So it matters quite a lot whether we're talking about pornography as commonly understood (but what's the legal definition?), or basically any sexually explicit material. What does Poem want to ban? Does he want to ban Eyes Wide Shut? That question isn't an argument at all, but it's rather important in order to clarify what the argument is.