8 U.S.C. § 1282: Conditional permits to land temporarily

the period of time (not exceeding twenty-nine days) during which the vessel or aircraft on which he arrived remains in port, if the immigration officer is satisfied that the crewman intends to depart on the vessel or aircraft on which he arrived; twenty-nine days, if the immigration officer is satisfied that the crewman intends to depart, within the period for which he is permitted to land, on a vessel or aircraft other than the one on which he arrived; or intends to depart, within the period for which the crewman is permitted to land, on the same vessel or on a vessel or aircraft other than the vessel on which the crewman arrived; and will perform ship-to-ship liquid cargo transfer operations to or from any other vessel engaged in foreign trade during such period. Pursuant to regulations prescribed by the Attorney General, any immigration officer may, in his discretion, if he determines that an alien is not a bona fide crewman, or does not intend to depart on the vessel or aircraft which brought him, revoke the conditional permit to land which was granted such crewman under the provisions of subsection (a)(1), take such crewman into custody, and require the master or commanding officer of the vessel or aircraft on which the crewman arrived to receive and detain him on board such vessel or aircraft, if practicable, and such crewman shall be removed from the United States at the expense of the transportation line which brought him to the United States. Until such alien is so removed, any expenses of his detention shall be borne by such transportation company. Nothing in this section shall be construed to require the procedure prescribed in section 1229a of this title to cases falling within the provisions of this subsection. Any alien crewman who willfully remains in the United States in excess of the number of days allowed in any conditional permit issued under subsection (a) shall be fined under title 18 or imprisoned not more than 6 months, or both.