Grey Water Dumping

I've been at campgrounds in California where not only is it permitted they actually have signs requesting that you dump it on trees in the campground. I can't speak for every state, but there is no general law in California prohibiting grey water dumping. There would be rules specific to campgrounds and I would never dump in a campground that didn't specifically permit it, but I have dumped on the ground when boon docking. I bet if people actually checked the wording of the laws they claim exists, most states probably do not have a broad law against dumping grey water, but instead it would be location specific.