Check out these articles, particularly for Colorado skiers:
Near the bottom talks about inverted aerials.
This is the Colorado Ski Safety Act. Look especially at 34-44-109, 34-44-110, and interesting enough, the limitation of liability ("tort reform") section in 34-44-113.
From what I have learned and studied in my legal education, ski resorts are near untouchable (of course there are always exceptions). You assume the risk, but that does not mean they cannot put warnings up or limit activity on their property. Just as in warning signs talking about "avalanche danger", "non-patrolled area," etc. All this terrain is within their property, but they still have the right to limit it. They want us to have fun, but you got to remember the idiots out there that cause us to have our "rights" limited. It only takes one to screw it over for all of us. As y'all would call it, the gapers out there ruin it for us.