. . .so they say.
I don't have a lot of energy for this right now, so I'll just give a brief overview.
The term "space marine" has a long history in science fiction literature, it being the term employed to describe Marines who serve on spaceships (duh). Possibly the term goes back to the Lensman (by E.E. "Doc" Smith) books, published in the 1950s. It may be older, since the old pulp magazines were big on what's now called Military SF.
Enter Game Workshop, which publishes a game called Warhammer, and has begun selling books and ebooks about Warhammer-specific "space marines."
Game Workshop has had at least one book using "space marine" in the title pulled from Amazon.com, because the work "infringes on its trademark."
Amazon, which remains Quite Ignorant about most common practices in publishing, pulls the book. Of course, when Amazon pulls your book, and you're an author, there is no appeal. There is no way to talk to Amazon, no way to get a review, and no one I've ever heard of has ever had a book reinstated, once pulled.
Pressed, Game Workshop claims to have a trademark on "space marines" in games only (which also Makes No Sense; the first use of "space marine" in gaming being 1977 when a game issued by FanTac was titled...wait for it: Space Marine).
They back-pedal a little, and say that they have a trademark in the European Union, which immediately became relevant in the United States when they began publishing novels and ebooks about Warhammer "space marines."
This is, to say the least, a very large case of stupid, and an author is wrongly losing income because of Game Workshop's willful lack of understanding. More worrisome is that they have said that they will aggressively protect their mark (as they should, if they have a mark that is actually, yanno, valid), so I'm guessing that all of us who have ever used "space marines" in a novel or short story are in Big Trouble Now.
For the curious, that list would include, but not be limited to, Robert A. Heinlein, Elizabeth Moon, and David Weber.
...and MCA Hogarth, the author whose book was pulled, who cannot afford a lawyer, and who really doesn't need this kind of nonsense in her life right now.