This is a problem Project Gutenberg has had for years, on Amazon and other platforms. It's a game of whack a mole and ultimately not really worth pursuing. As soon as you shut one guy down, another one appears with the same great idea.
In any case almost nobody is buying these anyway, as there are so many other free ebook editions of just about all of these books already.
I'm not a lawyer, but I believe failure to defend a trademark is a great way to lose a trademark.
I'm surprised Kobo doesn't have a list of banned seller names for situations like this. It would take zero effort on their end, and they're clearly opening themselves to liability.
Off to create Amazon and Disney stores over there... /s
In any case almost nobody is buying these anyway, as there are so many other free ebook editions of just about all of these books already.