What Is the Legal Distinction between a “Security” and a “Commodity” in US Regulation?

In the US, the SEC regulates "securities" (e.g. stocks, bonds, investment contracts), while the CFTC regulates "commodities" (e.g. gold, oil, and Bitcoin futures). The distinction hinges on the "Howey Test" for securities.

Bitcoin itself is generally treated as a commodity, which determines which regulator oversees its derivatives.