The rule they are breaking, is that when you google for an image and they show the image, then you click through to the page.. the image is not shown. If it shows a bunch of images and you scroll down to see more it requires you to login and I never got any further than that because its just annoying, but one of the reddit users says you even have to search for the image with the original search terms again but on pinterest.
Even if you're logged in there's a good chance you won't be able to find the image at all. Due to outdated Google index or some other issue I'm not sure...super annoying though.