Cal. Health & Safety Code § 443.20

A person who has custody or control of any unused aid-in-dying drugs prescribed pursuant to this part after the death of the patient shall personally deliver the unused aid-in-dying drugs for disposal by delivering it to the nearest qualified facility that properly disposes of controlled substances, or if none is available, shall dispose of it by lawful means in accordance with guidelines promulgated by the California State Board of Pharmacy or a federal Drug Enforcement Administration approved take-back program.