California Code, Government Code - GOV § 31779.2

If the program is modified pursuant to paragraph (2) of subdivision (b) of Section 31779, participants who entered, or who were eligible for, the program prior to the effective date of the modification shall be entitled to elect whether to become subject to the modified provisions of the program or to remain subject to the program as it existed on the participant's deferred retirement calculation date or election date, whichever occurred first.