I asked F&W for clarification and this is what I got:
Dear Greg,
Thank you for contacting the U.S. Fish & Wildlife Service (FWS), Office of Law Enforcement (OLE).
Your inquiry may have not received a response. If so, I apologize for the late or duplicate response.
To our current knowledge nearly all killifish species endemic to Brazil are protected under Brazil's list of endangered species law and are prohibited in trade. Without knowing the species, we can't say with absolution that the killifish were not legally acquired. Therefore, any such species that can be confirmed by Brazil to never have been allowed in trade, or legally exported from Brazil for commercial purposes would be considered an unlawful import and a violation of the U.S. Lacey Act, no matter the source or what country it is exported from.
Even if the killifish were inspected and cleared by FWS, it does not certify legality under U.S. law Per 50 CFR 14.52(a) which states (a) Except as otherwise provided by this subpart, a Service officer must clear all wildlife imported into the United States prior to release from detention by Customs officers. A Service officer must clear all wildlife to be exported from the United States prior to the physical loading of the merchandise on a vehicle or aircraft, or the containerization or palletizing of such merchandise for export, unless a Service officer expressly authorizes otherwise. Such clearance does not constitute a certification of the legality of an importation or exportation under the laws or regulations of the United States.
If you have additional information please let us know or the details can be submitted to the tip line,
https://www.fws.gov/wildlife-crime-tipsKindest Regards,
Wildlife Inspector Katrina Beihl
So, they're still banned, you still can't keep them, and it doesn't matter if they somehow got imported commercially and passed inspection. It doesn't matter whether or not you cross state lines. Still illegal. Don't bring any to the Convention.