He sold the rights to the book, and when he does that he effectively loses control of what the authors want to do with it for the screen. It was egregious with 'Clear and Present Danger'. They left some of the best parts of the book out of that movie! I loved the characters of Portagee, and Buck, and Buck's family. The family would have been a great story line in a movie, but now they can't use them because no one would know who they are!
I may have to go see the movie anyway, but I'll re-read the book first!
I think at this stage he could have maintained some creative control. Maybe not for the first one, but surely later. They need content in Hollywood.
Maria von Trapp signed away all rights to her story, so people made millions and she was powerless. But she did that willingly, yet complained later. "The Sound of Mucous" was first a hit in German, then copied in English.