Laws on permits for animals vary from state to state, which is how it should be. I happen to live in what I consider to be a good state in that regard, PA. Equating the situation in this country with the one in GB is apples and oranges because of the way our govts are structured. But I assume that when people call for a ban in this country that they are talking about a federal ban, which is totally beyond the authority of the feds.There are many laws for regulating behavior that are necessary and desirable. Fines for littering, mandatory recycling. I'm sure these impinge on individual liberties to junk up the planet and fritter away resources, but most of us agree that it is worth it!
There are plenty of reptiles and mammals that require a permit for captive care, not such a stretch to think it could/should be made applicable for certain fish.