Cal. Educ. Code § 23401

The board may require any member who retired for disability, prior to July 1, 1972, and who has not attained 58 years of age, to undergo a medical examination. If the examination, together with other available information, shows to the satisfaction of the board that the member is no longer disabled, the retirement allowance shall be terminated. Should any member retired for disability refuse to submit to medical examination, as provided in this section, the disability retirement allowance shall be terminated and all rights of the member in the disability retirement allowance shall be revoked.