I just went on a tour of a brand new aquatic teaching facility in the Des Moines school district as part of a tank tour with our Reef Society. The gentleman who heads up that department gave us the tour, and he used to be the head aquarist for the Blank Park Zoo in Des Moines. We had a discussion that interesting enough covered this exact topic - Asian Arowana. He has worked closely with the Fish & Wildlife Department, they would call him to the airport every time something came through that needed to be confiscated basically. I asked him point blank about your question and his response was that they are flat out illegal to own in the US. He also said that the only way that anyone could ever get in trouble is if it was reported. As an example, there is a nail salon on the south side of town here that has a big Red Arowana right in the front display of their store, and the F&W officer drives by it all the time, but he can't do a darn thing about it since no one has reported it to him.
So I think this basically answers your question. You cannot own them. I did not ask him if they were legal to own pre-ban, however you would probably have to prove that, and you certainly couldn't sell one in that situation or buy one that is currently 'grandfathered' if there even is such a policy.
My tanks: 120 Reef w/L2 Algae Scrubber, 60 Reef Pond w/floating Algae Scrubber, 40 Breeder Reef w/L2 UAS Tester Algae Scrubber
I maintain: 144 SW Reef w/L2 Algae Scrubber | 200 SW Reef w/L4 Algae Scrubber
Special knowledge: Algae Scrubbers, Acrylic Fabrication