My Epic Ski pass allows me to ski the Vail resort as well as many others. I ski Heavenly in South Lake Tahoe every couple of days. I asked some of the local Ski Patrol if I could bring my drone and fly it in some of the backcountry after I got off the lifts and skied away from other people. One of the guys told me I could probably get away with it during the slow times, but if they did catch me I would be asked to land and leave. I dont want to risk having my pass suspended for any time currently, but the end of the season is on the 22'nd of this month. So I may just fly at the resort closer to that date so if there was a suspension it would not really matter.
I would plead ignorance as there are zero signs prohibiting and nothing about it on thier website when I search. So if we are supposed to know that its disallowed then they certainly dont readily publicize it.