"Banned books!" is a phrase used for marketing, but it's not really accurate. Most, if not all, of the allegedly "banned books" aren't "banned" in the sense that you are implying, and the "banning" isn't being done by the fedeeal United States government. You can go to bookstores and see entire sections of "banned" books, which as you might guess from the fact that they are freely sold are not in fact really banned.