Here where I live, there's no such thing as Animal Control, it's handled by the Sheriff's Dept. Horses are also considered livestock, not petstock, and as such are property to pretty much be dealt with as you please. It would take skeletal horses and probably a couple of dead ones laying in the pasture before the Sheriff would seize them as they have no place to put a seized animal that size.
So, while I'm grateful to not live in an area anymore where the ACO was as crazy as the OP's visitor, I also wish we had SOMETHING that passed for Animal Control. There are conditions that really do benefit by them, even when they're being a PITA.