Buncha germans made a Warhammer movie. Games Workshop would love to let them show it. But can't - because under german law (where the people are) they have inalienable rights which would mean they ended up owning some of the ownership of Warhammer. Which, strangely enough, GW aren't willing let them have.
here
Andy Jones, legal and licensing head for Games Workshop, said this law confers rights on the creators of works that cannot be given away.
This means that the creators of Damnatus cannot assign their rights to Games Workshop even if they wanted to.
But by sanctioning the release of the film without this "assignment" Games Workshop would essentially be giving up the title to the Warhammer 40,000 intellectual property.
here