I was skiing the bumps on Prima at Vail with my 195 cm Rossignols in the late 1970s. I took the Pronto turnoff and stopped about halfway down to watch a guy telemarking with leather boots, wood XC poles, and wood or fiberglass kick-and-glide skis. The guy was doing telemark jump turns to navigate the 2-foot moguls. He was having fun doing his thing.
Fast forward 37 years.
2 guys who are expert XC telemark skiers want to telemark intermediate groomed terrain at Mt. Bachelor with their skate skis. It is not legal because their skate skis are not metal edged. Their skis might not bite enough during a turn which might cause them to lose control, fall, and slide into someone.
A gang of 6 skateboarders age 15 to 17 from Bend want to do some boarding at Mt. Bachelor. They want to race down intermediate hills using skiers as gates to practice snowboard giant slalom racing. This is legal.