Cal. PROB § 282

(a) Unless the creator of the interest provides for a specific disposition of the interest in the event of a disclaimer, the interest disclaimed shall descend, go, be distributed, or continue to be held (1) as to a present interest, as if the disclaimant had predeceased the creator of the interest or (2) as to a future interest, as if the disclaimant had died before the event determining that the taker of the interest had become finally ascertained and the taker’s interest indefeasibly vested. A disclaimer relates back for all purposes to the date of the death of the creator of the disclaimed interest or the determinative event, as the case may be.

(b) Notwithstanding subdivision (a), where the disclaimer is filed on or after January 1, 1985:

(1) The beneficiary is not treated as having predeceased the decedent for the purpose of determining the generation at which the division of the estate is to be made under Part 6 (commencing with Section 240) or other provision of a will, trust, or other instrument.

(2) The beneficiary of a disclaimed interest is not treated as having predeceased the decedent for the purpose of applying subdivision (d) of Section 6409 or subdivision (b) of Section 6410.