Rules to writing a fanfiction?

So, I was doing research for a fic and found on the author/creator's website that he has rules for people writing fanfictions. That certain scenarios and contexts aren't allowed due to the lore he has in place and will even take legal action to get it removed if a fanworks material is ever posted without his direct permission.

I don't really know how to feel about it to be honest. I've never thought of such a thing happening so I'm kind of flabbergasted.

I can't possibly see it legally holding up but...I don't know. Reminds me of the feeling I get when people tell me they've printed out my fanfic to read. I'm....not thrilled at the idea of a physical copy existing but it's really not a big deal to me at the end of the day.

I'm kind of curious what people think about it?