19 CFR §146.11

1. (a)From outside Customs territory. Merchandise may be admitted directly to a zone from any place outside Customs territory.
2. (b)Through Customs territory, foreign merchandise. Foreign merchandise destined to a zone and transported in-bond through Customs territory will be subject to the laws and regulations applicable to other merchandise transported in-bond between two places in Customs territory.
3. (c)From Customs territory, domestic merchandise. Domestic merchandise may be admitted to a zone from Customs territory by any means of transportation which will not interfere with the orderly conduct of business in the zone.
4. (d)From a bonded warehouse. Merchandise may be withdrawn from a bonded warehouse under the procedures in § 144.37(g) of this chapter and transferred to a zone for admission in zone-restricted status.