Nitrous is 50 state illegal on any public highway without a permit.
* Highway is considered any public road/street.
federal law not state.
Excellent.
So is Marijuana. and being in the country illegally.
When i lived there most cops were Citadel graduates. So when you get pulled over and the cop asks about your Nitrous, you ask him "did you go to The Citadel?" If he says "yes", but then hassles you about your Nitrous, politely inform him that is a federal law and not a state law and then slip this into the conversation: "...didn't you boys fire on Fort Sumter?"
I bet he lets you off with a warning.