I think he got it backwards, that snomobiles create far more pollution.
What I don't get is: why not just pass legistation stating that snomobiles have to meet pollution standards similar to the standards for cars? Then the manufacturers would be forced to make 4 cycle engines common, which are far quieter, and I would have less of an issue with them.
But IMHO, I believe that rather than check snow park permits and writing tickets to climbers, rangers' time would be better spent ticketing snomobiles who go where they shouldn't.