"when I began working child pornography cases early in 1977, there were no child porn laws. We used obscenity laws to prosecute child porn. In 1978, Congress enacted a law that prohibited the production of child porn without proof of obscenity, but the law was limited to material produced for pecuniary profit. It wasn't until after 1982, when the Supreme Court held that child porn could be prosecuted without proof of obscenity, that Congress enacted laws aimed at noncommercial production and distribution of child pornography."
https://www.catholicnewsagency.com/...in-child-pornography-and-obscenity-cases