Legal Question in Wills and Trusts in California

Sure, as a power of attorney can be revoked at any time without having to state a reason. A POA can only be used when the grantor is unable to do the activity required. You are thinking of the situation of a conservator who is appointed to handle the person's assets because they are not mentally or physically able to do so themselves. A POA merely means that you can do something I want you to when I can not be there, such as signing a contract while the grantor is on vacation somewhere, etc.

Your father needs to spend several hundred dollars to go to an experienced attorney who handles trusts and estate work to find out what his options are, how to save estate and other taxes, and how to protect himself from what seems to be a fight among his children to wrest control of his assets from him. Most if not all of the meeting with the attorney should be with the children not present.