18 U.S.C. § 2279

Whoever, not being in the United States service, and not being duly authorized by law for the purpose, goes on board any vessel about to arrive at the place of her destination, before her actual arrival, and before she has been completely moored, shall be fined under this title or imprisoned not more than six months, or both. The master of such vessel may take any such person into custody, and deliver him up forthwith to any law enforcement officer, to be by him taken before any committing magistrate, to be dealt with according to law.