Copyright law. And in Europe at least a deeper moral right to be identified as the author of a work and to have a say in how it's used. For example, I would be

Copyright law. And in Europe at least a deeper moral right to be identified as the author of a work and to have a say in how it's used. For example, I would be very upset if my work was used in advertising, or a political campaign that I violently disagreed with. It's not a black and white issue and that's why this went to the lawsuit stage.