No, they are legal in the US - at least they are not listed under the Lacey Act, or in Florida's list of prohibited species.
They were insanely expensive last time I saw them imported, though.
They are not illegal to own but prohibited from export (to my understanding) so good luck getting anyone to bring them in. Very expensive fish and if they get flagged on their way out from wherever they're being sold from most likely the buyer will be out tons of money. Retail in the US would be anywhere from $3000-$6000 per fish
They were previously much more expensive.. esp since the natives had to smuggle them from Brazil to friendlier countries before export. Even 5 years ago, they were almost never offered for sale.