Time and again, the Federal Reserve’s expansions have come under fire, but Emre Kuvvet’s recent discovery (“Sun Shines on Fed ‘Doomsday Book,’” op-ed, Dec. 12) offers a fresh insight into how those expansions got off the ground. As Prof. Kuvvet notes, the Doomsday Book he unearthed “reveals a fascinating history of diverging perspectives on the Federal Reserve’s emergency powers.” Yet it is revealing not only for the Federal Reserve’s past actions.

The Doomsday Book is also revealing for the conversation around a U.S. central-bank digital currency, or CBDC. Most notably, as Mr. Kuvvet explains, “Instead of adhering strictly to clear legislative boundaries to justify its actions during financial crises, the central bank appears to ground many of its decisions in the New York Fed’s belief in the Fed’s discretionary authority … without explicit congressional authorization in some instances.”

This finding is of prime concern when questions loom around the Federal Reserve’s authority to issue a CBDC. Although some argue the Federal Reserve Act clearly prohibits individuals from holding accounts at the central bank, it shouldn’t be forgotten that the Fed based its CBDC discussion paper on an intermediated CBDC that would involve putting financial institutions in the middle of the process—effectively creating a legal gray area. Based on Mr. Kuvvet’s findings, Congress shouldn’t wait to establish clear and enforceable boundaries.