Person X gives Person Y the authority to trade person's X brokerage account and to take money out of the account for the benefit of person X. It is not a durable power.
After some time, person Y has good reason to believe that person X is no longer legally competent, in part, because two doctors have expressed that view. However, no court has ruled that person X is no longer legally competent. Has person Y lost his ability to trade for person X?