Thanks for posting the duties of skiers Nay. I was thinking the same thing when reading the law. Skiers have a duty to not be on closed trails. Ski areas only have a duty to mark trails as closed at each identified entrance. So, nope, we can't hike up a closed trail from below. And, no, we can't ski over from the side and say we never saw a sign because it was at the top. A closed trail is a closed trail and skiing one get's you a $1000 fine.
What doesn't seem to be as clear is the law around when a trail is partially closed, as in this case. There are just so many different ways a trail can be partially closed. It would be very difficult to account for them all in the law. That's why the use of a rope or fence is allowable alternative. In a case where it's not obvious, I would think a area should be required to rope off a closed area. Hopefully that's a little bit of case law that comes out of this.
I also think this is where the historic use of hiking up from the lower gate may be the deciding factor. I was doing it 20 years ago and the HS kid testified it was still common practice. Ski Patrol has seen skiers and tracks make that hike for literally decades. If at some point the didn't want people doing it, they should have put up a rope or sign.
I think that's about right. I'm still left with the nagging feeling that this is really ultimately about the age of those involved. I haven't heard an adult reason that hiking up to the area under the closed gate was anything but skiing a closed area, the rest being technicalities of portions of trails, practice of hiking, and whatnot. That's the "I know better, but I can get away with it anyway" argument, which is fine to argue in cases of ski patrol issued violations, but it is woefully inadequate for a serious injury or fatality. It is not fair to assign that level of reasoning to a child and the law itself draws no age distinctions at all. That seems a more basic problem than the extent of roping 'trails' that are actually open slopes.