It's true that lowering the legal age to purchase products would increase the supply of cigarettes. This is because lowering the legal age to purchase will give more people the opportunity to access the purchase of cigarettes.

A decrease in the legal purchase age will increase supply since more people are able and are permitted by law to purchase at their will. That means that the consumption rate of cigarettes will increase. If consumption increases, the amount supplied will also increase. However, the statement will only apply to places where the rule of legal age is wholly followed.