well just like you have to be 18 (sometimes 21) to enter a liquor store. a headshop is legally (on the permit) known as a tobacco supply store and you have to be 18 to buy tobacco. therefore you have to be 18 to buy a tobacco accesory. (aka papers and "water pipes") the store owners are just covering there asses. cuz if a cop or someone from the city walks in and theres a minor in your store there going to assume that your intent was to sell something to them. there just covering there asses guys