Asian arowanas are illegal to keep in the USA. It is an endangered species so a CITES permit is required for anyone looking to own one. These are given out to scientific researchers, public aquariums, and zoos, not hobbyists. CITES certified fish farms may be able to provide you with a captive bred specimen, however. The other types of arowana are legal to keep in the USA, though silver arowanas are banned in Oklahoma.