The US Supreme Court held that the state law was far too broad, largely because the law restricted adult access to materials that were inappropriate only for children.
It is clear on the record that appellant was convicted because Michigan . . . made it an offense for him to make available for the general reading public (and he in fact sold to a police officer)a book that the trial judge found to have a potentially deleterious influence upon youth. The State insists that, by thus quarantining the general reading public against books not too rugged for grown men and women in order to shield juvenile innocence, it is exercising its power to promote the general welfare. Surely, this is to burn the house to roast the pig.
. . .
We have before us legislation not reasonably restricted to the evil with which it is said to deal. The incidence of this enactment is to reduce the adult population of Michigan to reading only what is fit for children. It thereby arbitrarily curtails one of those liberties of the individual, now enshrined in the Due Process Clause of the Fourteenth Amendment, that history has attested as the indispensable conditions for the maintenance and progress of a free society.