It's not mandatory yet in CA, but the BOP recommends it. So I enforce it strictly. I wish they make it a law though so I can just post it at drop off or drive through so I don't have to explain why we need to see your ID when you drop off a controlled script.
I would only make exceptions for expired IDs if they are regular patients and you know them well (but tell them next time you can't do that). Otherwise, see ya.