I don't know about WA, but in Colorado we can call the State Veterinarian's
office which is part of the Dept. of Agriculture. You might check into that.
Otherwise, I would do as someone else recommended and call the media. Problem is
you aren't supposed to trespass to get pictures. But if you can see the horses
from the road or someone else's property it is perfectly legal to do so. I would
definitely raise hell until someone responded.