A puff? Bwahhaha. Hey, I'm gay but that's one thing I've never been called.
Anyway, on the subject... Poppers were made illegal to sell back when AIDS was ravaging the gay community because they weren't sure what caused the immune deficiency problem and they were trying to eliminate the possible sources.
Lots of things are illegal to sell if the "intent" is to use them to get high. You will see several things sold as VCR head cleaners online and in sex/head shops. Ethyl chloride and any number of nitrate/nitrite solvents are included. The same thing applies to those research chemical sites. Selling Foxy, 2CT7, etc as a drug is illegal under the analog act, but selling them as research chems is a loophole which hopefully wont be closed anytime soon.
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"the pure and simple truth is rarely pure and never simple" Oscar Wilde