We had a nice thread about them here on the forum several months ago and some very nice pictures of the breeding habitat. Try doing a "search" on the forum for fly river turtle.
Anyone offering small Fly Rivers are selling Illegally laundered animals........Only a few Institutions and one or two private individuals have produced captive bred offspring, and those places have been working with the animals for 20+ years.........
EricIvins is right, if you are in the US that is..
FRT are ridiculously hard to take care of, due to how big they get. (They get up to 22" , which is very hard to manage for an aquatic.)
It'd make since that they are available for sale and trade in Australia, where they are from. But there are several laws against having them come into the US.
Actually owning one is not illegal in any way, just very difficult to do and take care of.
They are considered "Vulnerable" on the Endangered list, and have seen a 50% decline in the past 20 years.