Is federal obscenity law enforced? I doubt it can be enforced either, with the decision in Reno v. ACLU that struck down similar provisions of the Communications Decency Act as violating the First Amendment.

> If it's illegal to posses something, the government can ban offering to sell and distribute it.

This is begging the question, because first you would have to show that banning the mere possession of adversarial images doesn't violate the First Amendment. Otherwise you can make it illegal to possess books in a way to prevent the sale and distribution of literature.