They can if they own the rights - only artists can create art. A corporation is not an artist so cannot create art.
Ian Fleming was an artist who created the fictional character James Bond. No corporation can legally take his creation from him.
Let me give another example: Disney does not own The Force Awakens (2015). The person who created that piece of art owns it, in this case JJ Abrams. Disney doesn't actually own Star Wars. It's creator, George Lucas, does.
Yes, I know Disney paid Lucas 4 billion dollars for the franchise but ownership of a piece of art stays with the creator of that art.
What Disney can do is sue anyone else that makes a product for sale and tries to call that product 'Star Wars'. Only Disney can legally sell Star Wars products. But the ownership will always be the intellectual property of George Lucas.
Here's another example: George Lucas created Han Solo. So, because Disney bought the franchise from Lucas, Disney can hire a film-maker to put out a Han Solo film (which they did). But Disney cannot just decide to make Han a black woman.
What Disney could do is hire a film-maker to create a film with a female outlaw/pilot type character. But it wouldn't be Han Solo. And if that happened this new female character would be the intellectual property of the person who created him.