Well, there's that Constitution thingy.
I forgot about that -- what did that amendment say? "The right of the people and their children to be exposed to smut, pornography, and vulgarity shall not be infringed."
Actually, the origigal Constitution and BOR as written and ratified allowed each state the power to restrict this crap. You can thank (and maybe you will) the 14th amendment for giving the federal government the power to decide for all states what is protected by the 1st amendment (including the "freedem of expression", defined as being able to spin one's sagging breasts in different directions).