its a moral problem and a hard one.

i think there are, generally speaking, two types of a answers. on the one hand, you defer to the elders in a society. no matter what, those who have lived the longest have the highest authority. this is hard for westerners to conceptualize, but it is truly the case in some places. on the other, you defer to to doctrine (religion, law or constitution), which requires building up systems of interpretation and enforcement (legal proceedings, police etc.)