Legal positivism, by contrast to natural law, holds that there is no necessary connection between law and morality and that the force of law comes from some basic social facts. Legal positivists differ on what those facts are. (Soper, "Legal Positivism", Cambridge Dictionary of Philosophy)
In his book Law's Empire Dworkin attacked Hart and the positivists for their refusal to treat law as a moral issue. Dworkin argues that law is an 'interpretive' concept, that requires judges to find the best-fitting and most just solution to a legal dispute, given their constitutional traditions. (Ronald Dworkin, Law's Empire (1986) Harvard University Press)