you do have the right to make nearly every decision regarding your family.
and if you really don't want your kid to wear a helmet, then either a.dont let them snowboard or b.dont bring them to resorts. i can't think of a single responsible parent who wouldn't encourage their child to wear a helmet anyway, and now when they say "i dont want to, its not cool" you say "it doesnt matter because its against the law not to" in the same way they must wear a seatbelt, in the same way they must be a certain height to ride a roller coaster, etc.
Already stated that I don't mind the helmet law directly to you
. It's not the helmet law specifically. It's the fact that they use time and money add regulations such as this and since you seem to not understand why, I'll help.
Banks and financial firms have been having regulations lifted for decades now and once they blow everything, not only are they neither taxed nor any of the people punished, but they are given billions of dollars. Laws will be passed to add more trivial regulation on individuals and they will nickel an dime the hell out of people over these insignificant (as far as widely affected population is concerned) "infractions" of the law. There have been HUGE infractions of the law that have affected the entire world and no one is held accountable. But they'll fine Johnny when Johnny Jr isn't wearing his helmet. AND they won't let little Johnny eat what he wants for lunch.