Reports in talk.politics.guns indicate that the Louisville, KY BATF has informed a non-FFL (i.e., not a gun dealer, thus not under BATF jurisdiction in the matter) Army-Navy store's proprietor that it would be "shut down" if he did not remove from sale some Paladin Press titles on illegal conversion of firearms.
According to followups, it's worse: The State of Michigan has outlawed such texts for some time now.
Has this law ever been challenged in court? I doubt if it would stand up, as long as the books are written as "here's how one would..." rather than actively encouraging you to do it. Technical information cannot be banned, as long as you aren't inciting violence. In any case, here's a good use for the nets and anonymity. Scan those books, OCR the text, keep the graphics, and put them up for ftp or setup an anonymous mail server to mail them out. Technology can make such censorship impossible, but only if we use it. --- Mike