“A worm is either assur or muttar, as a swordfish is either a dag tamei or tahor, neither can be kosher some places but not others. “
Sorry, but I believe you are wrong about that. My friend’s mom came from Ireland, where the locally caught variety of tuna fish is NOT kosher (question about the scales). So her family has never permitted the eating of ANY tuna fish, even with a reliable hechsher, in the USA. Some things CAN be kosher in some places but not in others.