Originally Posted by
nako
Persons traveling from certain US territories (such as the US Virgin Islands) to the US mainland are subject to customs, immigration, and agriculture checks.
Mike
And here are the complexities of the Territory of Guam and the Commonwealth of the Northern Mariana Islands (CNMI):
Jurisdictions and background:
(1) Customs: Guam and CNMI (Rota, Tinian, Saipan) are both outside US customs zone, and have their own customs.
(2) Immigration: CNMI has its own immigration, but Guam is under US, hence CBP = "Not Customs but just Border Protection". For a US citizen traveling from Saipan to Guam, since you haven't left US soil, passport not required by USCBP Guam, just ID.
(3) Airport Security: If it's a US airport, it's TSA's job. However, for a long while, Tinian and Rota are too small to staff TSA people, so passengers from Tinian and Rota get checked by TSA upon arrival at Guam and Saipan.
The tale (when you fly Guam-Rota-Saipan):
At Guam, you go through the TSA check. Arriving at Rota (your first port of entry into CNMI), you go through CNMI immigration and customs. However, by using the "unclean" (in TSA's view) airport of Rota, you go through TSA again at Saipan before being let out to the streets.