California Code, Probate Code - PROB § 4231

(a) Except as provided in subdivision (b), in dealing with property of the principal, an attorney-in-fact shall observe the standard of care that would be observed by a prudent person dealing with property of another and is not limited by any other statute restricting investments by fiduciaries.

(b) An attorney-in-fact who has special skills or expertise or was designated as an attorney-in-fact on the basis of representations of special skills or expertise shall observe the standard of care that would be observed by others with similar skills or expertise.