46 CFR §24.05-1

1. (a)This subchapter is applicable to all vessels indicated in column 5 of table 2.01-7(a), and is applicable to all such U.S.-flag vessels, and to all such foreign-flag vessels, except as follows:
   1. (1)Any vessel operating exclusively on inland waters which are not navigable waters of the United States.
   2. (2)Any vessel while laid up and dismantled and out of commission.
   3. (3)With the exception of vessels of the U.S. Maritime Administration, any vessel with title vested in the United States and which is used for public purposes.