We just discovered you can camp for free (or, in some cases, damn near free) on Bureau of Land Management land. I don’t know about this horse business, though. From what I can tell, the BLM is all about helping the horses. (See here.)
(PS: The title is a reference to a Far Side cartoon. I couldn’t find a reproduction, so I’m going by memory here, but… In a cartoon entitled "Horse Hospitals," we see a bunch of horses on beds in a hospital with their legs in casts suspended above them. There are several doctors walking around, charts in hands, with shotguns tucked under their arms. The horses all look terrified. There’s one bed with the curtain drawn around it, a horse’s bandaged leg is sticking out from behind the curtain along with the word "BLAM!" How appropriate that you only have to add one extra letter to BLM?!)