The owner of the image are who have to decide the uses of their images. "All rights reserved" means that: the owner have rights for any use of images now and whatever someone invent in the future.

In an ideal world, each image of a dataset used in machine learning have to be identified with author and license. But I understand that is difficult to achieve because images are copied in the www and it is difficult locate the original source.

So, I have no doubt about the illegality of use images from web scrapping. Other thing is how easy is win/loss a lawsuit and to prove you used that data or not.