(a) Persons arriving from foreign countries are divided into two classes for the purpose of these regulations, first, residents of Guam and second, all other persons.

(b) Personnel of the Armed Forces of the United States ordered to duty in Guam or to any U.S. ship stationed at Guam are
classified for customs purposes as residents of Guam effective from date of reporting for duty.

(c) Any United States citizen coming to reside in Guam for a period of longer than thirty days will be regarded as a resident of Guam for the purpose of customs regulations.

SOURCE: GC § 47101.