California Code, Government Code - GOV § 31733

If a disability beneficiary is determined by the board to be no longer incapacitated and re-enters the service of a public agency covered by the retirement system under which he retired, his disability retirement allowance shall cease immediately upon such re-entry.  If such disability beneficiary again becomes a member of the retirement system, his rate of contribution for future years is that established for his age at the time of his re-entry into the system.  His individual account shall be credited with an amount which is the actuarial equivalent of his annuity at that time, as based upon the mortality table adopted by the board of supervisors for disabled lives, less any amount that has been refunded to him under Section 31737.  The amount shall not exceed the amount of his accumulated contributions at the time of his retirement for disability.  He shall also receive credit for his service as it existed at the time of his disability retirement.