Cal. RTC § 19393

(a) Except as provided in subdivision (b), for the purposes of the tax imposed under Chapter 2 (commencing with Section 23101) of Part 11, if any deduction, credit, or exclusion provided for in Part 10 (commencing with Section 17001) or Part 11 (commencing with Section 23001) is finally adjudged discriminatory against a national banking association contrary to Section 548 of Title 12 of the United States Code, or is for any reason finally adjudged invalid or discriminatory under the California Constitution, or the laws or the Constitution of the United States, the tax of the favored taxpayer shall be recomputed by the Franchise Tax Board for the taxable year in question, as of the time of allowance of the deduction, credit, or exclusion, by disallowing the deduction, credit, or exclusion, and any difference between the amount of the tax as recomputed and the amount of the tax as originally computed shall be subject to the provisions hereof relating to original computations.

(b) Subdivision (a) shall not apply to a taxpayer for the invalidation of any provision of Section 17053.98, 17053.99, or 23698 amended or added by the act that added this subdivision.