In addition to the reasons I cited above for central bank involvement in supervision, there is the issue of systemic risk and the fact that it is primarily the Federal Reserve’s obligation to maintain stability in our financial system BIS Review 36/1997  -5-  and that system’s interface with international financial markets.
This obligation cannot be met solely via open market operations and use of the discount window, as powerful as these tools may be. Financial crises, when they occur, are unpredictable and diverse in nature. Globalization means that a domestic crisis can become international or that a foreign crisis can become a domestic concern.