hello99,
Actually, halachah IS regional and has been for thousands of years; different parts of the world follow their own rabbis. You can see this in the gemara where rabbis from Eretz Yisrael would differ from rabbis in Bavel. And that remains the case today. For example, Italian Jews eat swordfish and have for generations; who am I as an outsider to tell them that generations of their rabbis were wrong? Yemenite Jews eat locusts; do you have a problem with that?
I follow the rabbis of my community. I buy all my fish from the same kosher fish store that is certified by the local Vaad. There is absolutely no reason to question my local Vaad, which is very well respected.