My assumption is that they were banned in areas known to have problems with wild populations for a reason - such as it is always possible for a species to escape the odds and increase the population, and it can prevent people from traveling a fairly close distance to capture wild specimens, bring them home and mix them with captive raised, risk spreading disease, having them reproduce and increase populations which could end up being released near areas where they are already thriving....there also could be a small problem forming in the area, hence them being banned