46 CFR §67.19

1. (a)A coastwise endorsement entitles a vessel to employment in unrestricted coastwise trade, dredging, towing, and any other employment for which a registry or fishery endorsement is not required.
2. (b)If eligible for documentation and not restricted from coastwise trade by paragraph (c) or (d) of this section, the following vessels are eligible for a coastwise endorsement:
   1. (1)Vessels built in the United States (§ 67.97);
   2. (2)Forfeited vessels (§ 67.131);
   3. (3)Vessels granted coastwise trading privileges by special legislation (§ 67.132);
   4. (4)Wrecked vessels (§ 67.133);
   5. (5)Captured vessels (§ 67.134); and
   6. (6)Vessels purchased, chartered, or leased from the Secretary of Transportation by persons who are citizens of the United States (46 U.S.C. 57109).
3. (c)A vessel otherwise eligible for a coastwise endorsement under paragraph (b) of this section permanently loses that eligibility if:
   1. (1)It is thereafter sold in whole or in part to an owner:
      1. (i)Not a citizen as defined in subpart C of this part, or
      2. (ii)Not a person permitted to document vessels pursuant to 46 CFR part 68;
   2. (2)It is thereafter registered under the laws of a foreign country;
   3. (3)It undergoes rebuilding as defined in § 67.177 outside of the United States; or
   4. (4)It is a crude oil tanker of 20,000 deadweight tons or above, and after October 17, 1978, has segregated ballast tanks, a crude oil washing system, or an inert gas system installed outside of the United States as defined in § 67.3.
4. (d)A vessel otherwise eligible for a coastwise endorsement under paragraph (b) of this section loses that eligibility during any period in which it is:
   1. (1)Owned by a corporation which does not meet the citizenship requirements of § 67.39(c);
   2. (2)Owned by a partnership which does not meet the citizenship requirements of § 67.35(c); or
   3. (3)Mortgaged to a person not identified in § 67.233(b).