Prohibition does not work. It did not work with alcohol, it's not working now with marijuana, cocaine, heroin, or meth, and it wouldn't work with tobacco. Any time you ban a product a lot of people will buy anyway, you create a huge source of revenue and power for organized crime and much worse problems for society as a whole than the banned activity itself. And, in general, having laws that a large chunk of the population will break if they think they can get away with it undermines people's respect for the law, their trust of law enforcement, and the rule of law in society.