The government can destroy the assumptions on which many businesses are built, that are held as stocks in an investment portfolio. Move the goalposts to relation to international markets, and I will likely find how it applies to some other asset commonly found in investment portfolios, like perhaps the current values of some tax preparation companies.
Your original assertion was "...by buying NFA machine guns knowing the number is capped and the price is likely to only go up"
Later you said lower risk than many individual stocks. Maybe, maybe not depending on how we define things. But I do think it's quite possible for the price to go down.
