33 CFR §151.21

1. (a)Each oil tanker of 150 gross tons and above and each other ship of 400 gross tons and above, operated under the authority of a country not a party to MARPOL 73/78, must have on board valid documentation showing that the ship has been surveyed in accordance with and complies with the requirements of MARPOL 73/78. Evidence of compliance may be issued by either the government of a country that is party to MARPOL 73/78 or a recognized classification society.
2. (b)Evidence of compliance must contain all of the information in, and have substantially the same format as, the IOPP Certificate.