When it comes to understanding the legal validity of a law, it's important to consider the moral obligation of its subjects to obey it. This moral obligation requires a moral justification, so the real validity of the law is dependent on its moral justification. To gain a better understanding of this concept, let's take a look at three senses of the word “valid”: laws that are really valid because they deserve to be obeyed, laws that are legally valid because a particular legal system states they must be obeyed, and laws that are morally valid in the sense that they could be morally justified even if the legal system has not yet made them legally valid. The earliest rule of legal validity in the Western legal tradition can be found in Hesiod's religious poem Works and Days, which dates back to around 700 BC.
This rule states that no moral or legal code is truer than any other, and no person should assert their moral or legal judgments above those dictated by the state. Legal validity is closely linked to morality because it is one of the things that is commonly recognized as an ultimate determinant of legal validity. The separability thesis considers four statements only as contingent connections; they do not refer to all possible legal systems; probably not even to all historical legal systems. Legal positivism rejects the moral and historical dimensions of law as sources of law or standards of legal validity.
Legal custom provides a standard of legal validity that imposes customary limits on the coercive powers of the political ruler. This essay describes the cycle of legal validity in Western law and proposes a new approach to legal validity to break this cycle. The ultimate criterion of validity in a legal system is not a legal norm or a presupposed norm, but a social rule that exists only because it is actually practiced, that is, it is used to guide behavior. Legal positivism fails to provide an adequate explanation for why certain laws are legally valid while others are not. It also fails to take into account the moral and historical dimensions of law as sources of law or standards of legal validity.
In order to gain a better understanding of what makes a law legally valid, we must look beyond just the narrow philosophical method proposed by legal positivism. We must consider the moral obligation of its subjects to obey it, as well as its moral justification and its place within the cycle of legal validity in Western law. Only then can we truly understand what makes a law legally valid.