Upon reading the comments in another thread, one might get the idea that stock use in the Sierra Nevada is some kind of unregulated, free-for-all. In fact, pack station operators (including government and commercial outfits) are under very strict regulations. The following link to the Sequoia Kings National Park website details those regulations. It would be worth your while to read them. Please note that the regulations are much more strict than those for backpackers and hikers. Obviously, we hikers are quite a bit harder to monitor.

http://www.nps.gov/seki/planyourvisit/stockuse.htm

There are a few local concerned citizens who have taken upon themselves to covertly monitor certain Bishop area pack stations to make sure for themselves that the pack station operators are following the regulations. One particular pack station, near Bishop, has observed people hiding in the trees above the pack station, watching through binoculars the activity at the pack station. I guess they don't trust the Forest Service and the Park Service's monitoring. Perhaps this is a case of "environmental paranoia"...LOL.