AFAIK, MGC are federally prohibited in the US regardless of their origin, which is why importers sometimes have problems at the border with other similar-looking Pangasiidae, e.g., paroon shark catfish.
Just as thefredpit says, they, like Asian arowana, can be imported and possessed only with a permit for the importation and a permit for possession, which are given on a case by case basis only to institutions engaged in their research or education / public exhibition. The permits are not granted for use as a personal pet or other personal purposes.
