Federal tobacco laws and policies are implemented to ensure the health and safety of the consumers. They are also in place to regulate consumption of the product, therefore the best answers are:
Help people stop using tobacco products - done by placing certain restrictions on purchase of tobacco products, price inflation and tax increase of tobacco etc.
Limit the health effects linked to tobacco use - this is done by adding health warnings on packets of cigarettes.
Prevent youth from starting to use tobacco - this is done by making the legal age to purchase and smoke cigarettes 18 years old.