If the "character traits" are under copyright, and thus these shirts violate copyright, then how are the posters that the shirts are based on public domain? The

If the "character traits" are under copyright, and thus these shirts violate copyright, then how are the posters that the shirts are based on public domain? The posters contain the same character images, and even if they were not registered with the copyright office directly, I don't see why the claim on the shirts would not extend to the posters also?