In a game-changing development for the future viability of digital asset securities trading, staff of the Division of Trading and Markets of the SEC issued a No-Action Letter to FINRA on September 25, 2020 clarifying a structure under which registered broker-dealers could operate alternative trading systems that allow for real-time trading of blockchain-based securities, without running afoul of the custody requirements of Rule 15c3-3.  The structure was originally proposed to the SEC staff in a request for no-action relief from Davis Polk & Wardwell partners Annette Nazareth and Zachary Zweihorn on behalf of several clients, but the staff ultimately decided to issue the relief more broadly as industry-wide no-action guidance to FINRA.