It's perfectly legal to hike up Hood for turns. The area that the resort has set up is probably not legal to go ride without paying for a ticket or when they are doing pro shoots. It is perfectly within their rights to restrict access to that terrain and have you arrested for trespassing if they so choose. There is plenty more terrain than the glacier that they hold the ski/snowboard camps on and it's ok to access it to do what ever you feel like doing on it. Just remember that crevasses and other hazards exist higher up on that mountain. Stuff that can eat you up and never see the light of day again.