46 U.S.C. § 60303

(a) Imposition of Tax .— A tax of 50 cents per ton, to be called “light money”, is imposed on a vessel not of the United States at each entry in a port of the United States. This tax shall be imposed and collected under the same regulations that apply to tonnage taxes. (b) Exception for Vessels Owned by Citizens .— (1) In general .— Subsection (a) does not apply to a vessel owned only by citizens of the United States if— (A) the vessel is carrying a regular document issued by a customhouse of the United States proving the vessel to be owned only by citizens of the United States; and (B) on entry of the vessel from a foreign port, the individual designated under paragraph (2) states under oath that— (i) the document contains the names of all the owners of the vessel; or (ii) part of the ownership has been transferred since the document was issued and, to the best of that individual’s knowledge and belief, the vessel is still owned only by citizens of the United States. (2) Person to make statement .— The statement under paragraph (1)(B) shall be made by— (A) an owner if one resides at the port of entry; or (B) the master if an owner does not reside at the port of entry. (c) Exception for Vessels Becoming Documented .— Subsection (a) does not apply to a vessel that— (1) is owned only by citizens of the United States; and (2) after entering a port of the United States, becomes documented as a vessel of the United States before leaving that port.