Selling Handicap Parking Stickers

Economists believe that almost everything should be tradeable. That's why we mostly support allowing people to sell their kidneys. But what about handicap parking spaces? Imagine that a physically challenged person legitimately gets a handicap parking sticker for his car. Should he be able to sell it to an able-bodied person?

The handicapped person would only sell the sticker if the trade made him better off. If, however, the able-bodied person would make greater use of the sticker than its previous owner than the sale would impose costs on others and so perhaps should be blocked. But if there was some way of preventing the new owner from using the sticker more than its previous owner did then I would support allowing the trade to take place.