You don't need a license to own a car or to drive it on your own property or to transport it (without driving it) from point A to point B. A 10-year-old can legally own a car and can legally drive it on private land. It's only driving on public roads that requires a license. So if we regulated magnets (or, heck, guns) the way we regulate cars, anybody could buy as many as they wanted of the regulated product and use it pretty freely.