Some of the photos are selling for upwards of $100,000, but the original photographers will never see a dime.
Artist Richard Prince takes the Instagram photos and comments on them. He also may make minor changes -- but that's it.
The Instagram users say Prince never got their permission to use the images.
Attorneys say it's fair use, which allows artists to comment and change existing art work to create something different.
Attorney Jonathan Malki said, "We may not need to see as much transformation as you would think. Sometimes a relatively small change can be considered fair, if it creates a new expression."
Experts say the only way to really prevent someone from reusing your social media photos is by making sure your account is private.