“Freeports have an impressive history. They arose from the legal exemption that items ‘in transit’ receive from taxes and tariffs. It was expected that this exemption would only be temporary as shipped goods transferred between planes or were temporarily stored while awaiting shipment to their final destinations. But investors quickly realized another, more profitable use for them. Because there was no limit on how long something could be ‘in transit,’ freeports offered an innovative solution for avoiding taxes and tariffs on high-value assets. This system allows stored assets to appreciate in value, and it also allows for tax-free sales. Demand for space has surged to unprecedented levels.”
http://www.fee.org/the_freeman/detail/swiss-freeports-and-the-invincible-tax-evader