Cal. Educ. Code § 24004

In cases of a member’s willful substance abuse or if the board determines a member who qualifies for a disability allowance pursuant to Section 24001 has mental, physical, or vocational rehabilitation potential, the board may limit the disability allowance under this part to a period not to exceed two years from the date of approval of the disability allowance. Notwithstanding Section 24013, the disability allowance shall terminate at the end of the period granted unless an extension is granted by the board.