Others have provided information on axolotls, but I need to comment on the legality issue, as this is serious and there are some irresponsible suggestions being tossed around here (perhaps in jest...?).
It is easy these days for aquarists to find themselves becoming--in the view of outsiders to the hobby--lumped in with a group of individuals who are, frankly, degenerate criminals. I refer to those who "make money" out of the illegal trade of animals that in many cases are threatened if not close to extinction: the elephant ivory trade, the rhino decimation, the trade in exotic birds and reptiles that are disappearing in their habitats, etc.. We must therefore ensure we are not seen in this group, but rather as responsible human beings who care about and work for the protection of all species. There are projects in tropical areas that allow the controlled and responsible collection of ornamental fishes which provides what is a fairly good income for the indigenous peoples, while ensuring the habitat is not harmed, nor the species threatened.
Habitat destruction has taken and will continue to take a toll in many species of ornamental fishes, and some have already become officially extinct. Aquarists can ensure such species do not disappear, even if the species are only maintained in aquaria, public or private. Re-populating the habitat with a species no longer there is not usually possible, especially when the habitat itself is gone. But it is terrible to realize that we can easily lose these incredible species, some of which may not even have been discovered yet.
All of this is by way of saying that we must obey whatever environmental laws are enacted--they are there usually for good reason--and not be seen in the afore-mentioned group. In some cases, a state or federal law prohibiting species "x" may be intended to protect that species. In other cases, the law may be there to protect the local environment--irresponsible "aquarists" too often acquire this or that fish, amphibian, snail, plant, or whatever, and then lose interest and it gets dumped into the local watercourse. Sometimes, and all too often, the invader survives, decimating the local species. This has occurred in parts of the US and (I think) Europe with assassin snails wiping out the native species. We must strive to combat not only the actions of these people, but the perception we are somehow all the same. Even kidding about ignoring such laws in order to have "x" pet can have unfortunate consequences for the hobby and the fish/amphibians themselves.
