In the US you need an import license. You’d have to talk to your local dept of natural resources about how/if you can acquire one. Of course, it depends on the species you want to bring in as well. Obviously restricted or illegal species are off the list immediately. One option if it’s a 1 off thing is to locate a reputable transhipper to work with to acquire what you’re looking for. Rare Fish USA have an import license. Also, if you want Tanganyikan cichlids Hung Vo used to import for private sales