
I ski all the time with my Lab but cross-country and on bush trails, not at ski resorts. It is tricky on the downhills as she loves to run in front of me and do a big leap up in a circle in front of me. Several times she has misjudged my speed and I have had to straddle her on the way down. Good thing she is small for a Lab.
Ski resorts don't like dogs on the trails (or hills either I imagine) for obvious reasons; collisions with skiiers, holes in the trail from doggy feet and the dreaded "brown klister."