I think, agree that we don't want banks to take excessive risks when they have a safety net from the government, so the question is how do you control those risks?
The Volcker rule might be appropriate. You have to be careful that you don't inadvertently, for example, prevent a good hedging, which actually reduces risk, or that you don't prevent market making, which is good for liquidity.
One possibility is that, if you were to go in this direction, would be to give some discretion to the supervisors to decide whether a set of activities is so risky or complex that the firm doesn't have the risk management capacity or the managerial capacity to deal with it and then give the supervisor the authority to ban that activity. So there might be ways to do it using supervisors.
In response to a question about the Volcker rule during the Q&A session