PROB § 21392

(a) This part shall apply to instruments that become irrevocable on or after January 1, 2011. For the purposes of this section, an instrument that is otherwise revocable or amendable shall be deemed to be irrevocable if, on or after January 1, 2011, the transferor by reason of incapacity was unable to change the disposition of the transferor’s property and did not regain capacity before the date of the transferor’s death.

(b) It is the intent of the Legislature that this part supplement the common law on fraud and undue influence, without superseding or interfering in the operation of that law. Nothing in this part precludes an action to contest a donative transfer under the common law or under any other applicable law. This subdivision is declarative of existing law.