TITLE 46 - US CODE - SUBCHAPTER II - FORMAL SYSTEMS

46 USC 14511 - Application

This subchapter applies to a vessel described in section 14501 of this title if
(1) the owner requests; or
(2) the vessel is
(A) self-propelled;
(B) at least 24 meters (79 feet) overall in length; and
(C) not operated only for pleasure.

46 USC 14512 - Standard tonnage measurement

(a) The Secretary shall prescribe regulations for measuring the gross and net tonnages of a vessel under this subchapter. The regulations shall provide for tonnages comparable to the tonnages that could have been assigned under sections 4151 and 4153 of the Revised Statutes of the United States, as sections 4151 and 4153 existed immediately before the enactment of this section.
(b) On application of the owner or master of a vessel of the United States used in foreign trade, the Secretary may attach an appendix to the vessels register stating the measurement of spaces that may be deducted from gross tonnage under laws and regulations of other countries but not under those of the United States.

46 USC 14513 - Dual tonnage measurement

(a) On application by the owner and approval by the Secretary, the tonnage of spaces prescribed by the Secretary may be excluded in measuring under this section the gross tonnage of a vessel measured under section 14512 of this title. The spaces prescribed by the Secretary shall be comparable to the spaces that could have been excluded under section 2 of the Act of September 29, 1965 (Public Law 89219, 79 Stat. 891), as section 2 existed immediately before the enactment of this section.
(b) The Secretary shall prescribe the design, location, and dimensions of the tonnage mark to be placed on a vessel measured under this section.
(c) 
(1) If a vessels tonnage mark is below the uppermost part of the load line marks, each certificate stating the vessels tonnages shall state the gross and net tonnages when the mark is submerged and when it is not submerged.
(2) Except as provided in paragraph (1) of this subsection, a certificate stating a vessels tonnages may state only one set of gross and net tonnages.