(a) Admission without entry or payment of duty. Trucks, busses, and taxicabs, whether of foreign or domestic origin, taking out merchandise or passengers for hire or leaving empty for the purpose of bringing back merchandise or passengers for hire shall on their return to the United States be admitted without formal entry or the payment of duty upon their identity being established by State registration cards.

(b) Use in local traffic. Trucks, busses, and taxicabs in use in international traffic, which may include the incidental carrying of merchandise or passengers for hire between points in a foreign country, or between points in this country, shall be admitted under this section. However, such vehicles taken abroad for commercial use between points in a foreign country, otherwise than in the course of their use in international traffic, shall be considered to have been exported and must be regularly entered on return.