Motivation is irrelevant - this kind of law is intolerable.

You wanna limit it to current users? Say that. Have a national registry of whoever's bought them before, and if they stop for six months, they're off the list. Treat it like a progressive opioid program where the government supplies them directly by mail, if they fill out some preachy postcards.

Age limits are only legitimate because of physiological differences. A 12-year-old cannot be trusted the same way as a 22-year-old. But today's 22-year-olds are no different from next year's 22-year-olds. Or the next, or the next. Declaring some of them unfit is worse than baseless age discrimination. It is creating second-class citizens, forever barred from... whatever.

Allowing bad precedent for good reason would create tremendous problems later. People would propose all kinds of exclusionary bullshit, where old people get to do stuff forever and young people never will, and they'd excuse it by saying 'well you allowed it for smoking.'

If you think that'd never happen - I will remind you this law was defeated by assholes who think more people should smoke. So they can funnel more wealth to the wealthy. Good faith and sensible governance do not need more obstacles.