On July 25, 2017 the SEC published an investor bulletin concerning Initial Coin Offerings. In that bulletin the SEC discussed its report of investigation under Section 21(a) of the Securities Exchange Act of 1934 describing the SEC investigation of The DAO, a virtual organization, and its use of distributed ledger or blockchain technology to facilitate the offer and sale of DAO Tokens to raise capital. The Commission applied existing U.S. federal securities laws to this new paradigm, determining that DAO Tokens were securities. The Commission stressed that those who offer and sell securities in the U.S. are required to comply with federal securities laws, regardless of whether those securities are purchased with virtual currencies or distributed with blockchain technology.
The complete investor bulletin is available here: https://www.sec.gov/oiea/investor-alerts-and-bulletins/ib_coinofferings