Is a link with morality necessary for positive law to be valid law?

Extraits

[...] The law is linked with morality concerning its interpretation. Aquinas give an example of a law, which can be override depending on the situation, and more exactly, on the necessity of its application, necessity knows no (Jurisprudence, Penner, p62) C. Finnis John Finnis gives a conception of this 'common good' and think that we have to give it effect in the law. The purpose of the law is the achievement of the common good. The best explanation can be found in Jurisprudence, Penner, p 45 involves an exercise of judgement of human behaviour. [...]

[...] Saint Augustine add that “there is no law unless it be just” De Lib. Arbitrio, according the rule of reason. law which is not just cannot be called a law”. Our conscience by consequent, do not oblige us to obey an unjust law. These explanation had been used during the judgements of Nazi dirigeants. denying the connection between the practice of law and issues of ethics and justice, German lawyers impoverished the notion of law and abrogated their responsibility to resist the immorality of Nazi says Penner in Jurisprudence p 43. [...]

[...] Natural law theorists claim that the description of the law without including the moral or ethical element can only be incomplete. They give a great importance of the moral reasoning in legal practice. Legal matters can't be separated from ethics. We shall explore whether a link with morality is necessary for positive law to be valid law. The positivists admit that the law can be ethical but they affirm that ethical questions are not necessary linked with law. In that particular point, they differ from the Natural Law position which asserts the necessity for the law to be moral. [...]

[...] It insists on a distinction between human law, which they call positive law and moral laws. Hart believe that the validity of law is independent on its “equity or iniquity, its moral value or lack of it”(D'Entreves 1970, Essay A Core of Good Sense: Reflections on Hart's Theory of Natural Law, 185-203). He gives the examples of societies founded on evil laws which are still viable because maintain by the force. Laws can be created, and the basic norm specifies how they can be created and changed. [...]

[...] The law arise from the reason, “derived from nature, directing people to good conduct and away from crime” (Cicero, On the Laws, Book 8-15). Moreover, we have another proof in the “interpretation of the word 'law' [in which] there is a significance and intention of choosing something just and right”(ibid). B. Aquinas For Aquinas, the law concern the common good. Human law 'oblige in conscience'. If not, it is not a law. We can can see how, for Aquinas, the morality take place in the law. [...]