I think this will backfire on NZ. Banning things that people decide they want pushes the supply of that item into the hands of criminals.
Prohibition in the USA made the Mafia (and other gangs) very powerful, because lots of people still saw nothing wrong with drinking alcohol. And if the only place they could get it from was criminals, they dealt with criminals. It normalised dealing with criminals, gave the criminals a veneer of 'respectability'. And that has made it impossible to eradicate such gangs.
It's all very well saying you're banning cigarettes for the under 14s, but a 13 year old will be 18 in five years time. Are they still going to accept this when a 19 year old can legally buy them? What about when they're 25? 30? Will the law really look reasonable banning a 30-year-old from buying something a 31-year-old can legally buy? Really?
Are NZ banking on 'if they don't start at 14 they won't ever start'? It strikes me they really don't understand human nature. And show a bit of a totalitarian streak we should be wary of, because if they pass such a law, which product is next on their (potentially long) list?