One of the more ridiculous examples I have come across, unpasteurized milk. In the US, as well as Canada and other western countries I believe, it is illegal to sell raw milk for human consumption. Meaning that if I have a neighbor with a milk cow, I can't buy a gallon of milk from them to drink or cook with. Stores can obviously do what they want, and requiring FDA certification for example would effectively block raw milk from stores. But why can't I choose to ignore FDA guidelines meant for industrial milk production and just buy a damn gallon of milk from a local farm?