United States v. Williams (2008)
United States v. Williams, 553 U.S. 285 (2008), was a decision by the Supreme Court of the United States that a federal statute prohibiting the "pandering" of child pornography (offering or requesting to transfer, sell, deliver, or trade the items) did not violate the First Amendment to the United States Constitution, even if a person charged under the code did in fact not possess child pornography with which to trade.
Source: Wikipedia — United States v. Williams (2008) (CC BY-SA 4.0)