I think almost any type "aftermarket" accessory that you can buy, has a disclaimer of "for off road use only". Especially air/fuel/exhaust/ECM enhancements.
This supposedly covers the third party manufacturers butt. However the EPA did attempt a move towards the regulation of "off road" vehicles in the same aspect... but then withdrew. Here's just a quick link that I found remarking that:
http://yellowhammernews.com/politics...labama-racing/
21 years Army (retired)
...been everywhere, seen everything, done almost everything.
IBA 80537