Asian Arowana,
Scleropages formosus, are listed as endanged by the IUCN, and are listed under appendix 1 by CITES, which means they need special documentation to possess in signed countries (if you live in
Andorra,
Democratic People's Republic of Korea,
Federated States of Micronesia,
Haiti,
Kiribati,
Marshall Islands,
Nauru,
South Sudan,
Timor-Leste,
Tonga,
Turkmenistan, or
Tuvalu and can smuggle one in, CITIES can't do anything) The reason why you can't have them in the United States is the Endangered Species Act, which prohibits the possession, transportation, or propagation of listed species, except by Zoos and conservation programs. You cannot have one, the same way you can't own a California Condor. They are a foreign species, but that is in the Endangered Species Act to prevent Americans from buying Ivory, Tiger Skin rugs, or some rare parrot as a pet and so lead to extinctions. Should Asian Arowana be listed? probably not, people don't usually catch wild fish, they are from farms. Tigers, Rhinos, rare parrots, and elephants are not generally farmed as Asian Arowana are.
Jardini Arowana,
Scleropages jardinii, Looks basically the same, as they are both members of
Scleropages (remember the genus
Canus, includes Dogs and Coyotes which are very common, and people usually don't care about shooting a coyote, but
Canus also includes the Red and Ethiopian Wolf which are very rare, and would get a lot of attention if you shot), Jardini are not endangered, neither the IUCN or CITES even say they are threatened.
The other reason why captive bred Arowana should/cannot be returned to the wild is hobbyists like all the bright color morphs, that simply don't exist in wild populations, and would make wild fish especially fry susceptible to predation and so make them rarer. Most people want really bright fish that have been selectively bred like a Super Chili Red or Purple, or a deep Golden color. I myself really like wild type Super Reds, but that is my preference.