Cal. Pub. Util. Code § 12337.5
Notwithstanding the provisions of Section 12337, the retirement board may comply with and give effect to a revocable written authorization signed by a retired member or beneficiary of a retired member entitled to a retirement allowance or benefit under this chapter, authorizing the district to deduct appropriate amounts from the retirement allowance or benefit payable to any such retired member or beneficiary of a retired member for the purpose of paying premiums of any group medical or hospital service plan, or both, approved by the district, for the benefit of such retired member or his dependents, for the payment of personal income taxes to the Government of the United States or of the State of California, or for the purchase of shares in, or the payment of money to, the utility district credit union.
Ca. Pub. Util. Code § 12337.5