Replying to Is hiking a park illegal?

So whenever I'm home from school, I got to this mountain near my hometown and hike some rails at the bottom of the mountain.  This year they put up a sign that says a lift ticket and park pass are required for the "park".  The sign is facing the bottom of the mountain right on the hike to the park, so it's definately there for people like me...does anybody know if you can get busted for theft of services or something like that if you are just hiking rails and they ask to check your pass?