Harry acts as though there is nothing that can be done to stop Bull. However, Harry frequently holds individuals over for psychiatric evaluation at Bellevue because they exhibit signs of mental illness, and Bull's claims could easily be considered signs of psychosis.
Roz suggests getting an injunction to stop Bull before he gives everything away, which Harry shoots down, noting that giving away money isn't illegal. However, Harry should know that a conservator may be appointed to oversee the finances of a person deemed unable to do so for themselves.