I don't think it's often explicitly stated or even identified as a premise - the only case in which I see it stated by people who understand what it means is when restrictionists bring it up in debates about immigration. Its opponents call it tribalism, what its proponents call it differs depending on what the in-group is. I would classify it as a form of moral intuitionism. By the way, there are other ethical theories in addition to the three you mentioned. For example: contractarianism (though perhaps it's a form of consequentialism), contractualism (maybe consequentialist or deontological), and various forms of moral intuitionism.