That is not entirely correct.[1] The CFTC has authority to investigate frauds which affect commodity markets in which futures trading exists, and they have used this with regard to Bitcoin. "Examples of Prohibited Activities: Price manipulation of a virtual currency traded in interstate commerce.", writes the CFTC.

One could, for example, trade some art object at a grossly inflated price between two parties that are secretly cooperating. That's a "wash sale". Do that in a US-traded stock, and the SEC will go after you. Do that in a US-traded commodity, and the CFTC will go after you. Do that in a NFC, and you're probably legal. This is very convenient.

[1] https://www.cftc.gov/sites/default/files/idc/groups/public/%...