Maybe nicotine addiction should be medicalized.

Anyone born after [date] could get it legally through a pharmacy after talking to their doctor/nurse-practitioner and explaining why they need a prescription (ie they are addicted and can't function without it).

I actually like that framing. I'm imagining explaining it to my 5 year old:

What's that person doing?

They took the wrong medicine and now they have to take that medicine everyday. It's yucky, expensive, and very hard on their body.

Why did they take the wrong medicine?

They didn't realize it was medicine and they thought it looked interesting or fun, I'm not sure exactly. You know not to take medicine without talking to mum, dad, or a doctor right?