Cal. Gov. Code § 75030.7
Any judge has a right to elect, by written election filed with the Judges' Retirement System at any time prior to retirement, to make contributions pursuant to this section for, and receive service credit in this system for all of the time he or she served as a federal judicial officer, excluding any period of time for which the judge is receiving, or is entitled to receive, a retirement allowance from any other public retirement system.
As used in this section, the term "federal judicial officer" means federal justice, federal judge, and federal magistrate judge.
Every judge electing to receive credit for service pursuant to this section shall at the time of filing his or her election, pay into the Judges' Retirement Fund a sum equal to actuarial present value of the increase in benefit due to the additional service. The amount shall be determined by the Judges' Retirement System in accordance with this section.
Ca. Gov. Code § 75030.7