It is odd that a value/virtue that plays such a central role in dramatic literature has played such a small role in philosophical writing. There are probably a number of reasons, but I think that a predilection for a certain kind of individualism is a major one. Others might include the fashionability of consequentialism, the idea that loyalty has more to do with sentiment than reason, as well as its proneness to corruption. The revival of interest in virtue/character as distinct from rules/principles has also created space for a renewed, if hesitant, interest in loyalty.

Structurally I don't see a fundamental difference between what we may reasonably expect of police and doctors - though obviously the fact that doctors are generally pursuing life-saving activities and police may be engaged in life-threatening activities may lead to differences in how we construe the moral limits to their roles.

Loyalty saves us from the self-advantaging compromising of important relations - such as friendship, marital and professional commitments, group memberships, and so on. But as the Aristotelians would put it, its expression requires phronesis - wisdom not to allow it to compromise other important virtues ,there is something to the ancient doctrine of the unity of the virtues. I believe that is true of all virtues, but especially of the executive virtues - such as industriousness, sincerity, conscientiousness, and courage - which may become detached from substantive goods.

As a matter of ethics - our broader social life needs to be constrained by law and other devices - resolving at the societal level matters that should not be left for individual ethical negotiation. What is important - in the end - is that we are enabled to flourish in ways that acknowledge our dignity.

I grew up in a home in which loyalty to family was central to my father's outlook. Adolescent changes to my outlook (which set me against parental values) made me very critical of loyalty, reinforced by certain religious writers I found influential at that time. Harry Blamires, The Christian Mind. But I remained conflicted about loyalty.

Police do not work at the immediate direction of the communities they serve, but through their institutional connections. Police departments may develop structures, modi operandi, and cultures that are ethically problematic.

Whistleblowing constitutes a nice test case for the evaluation of loyalty. Loyalty also appears at the intersection of many major philosophical debates: general ones such as those between consequentialism and deontology, reason and feeling, virtue and principle, as well as more specific ones such as nationalism and patriotism, morality and obedience, particularism and universalism.