Hart fuller debate

Legal theorists can thus be divided into two schools of thought, those who adhere to positivism and others who subscribe to the natural law theory. The positivists like Hart and Austin, merely attempt to define what law is, not what it should be, or its content. The natural law theorists believe that rules or principles can only legitimately be called law if they conform to an acceptable code of moral behavior.
The Hart-Fuller debate is an exchange of ideas published in the Harvard Law Review in 1958 on morality and law
This demonstrated the divide between the positivist and natural law philosophy. Hart took the positivist view in arguing that morality and law were separate. Fuller's reply argued for morality as the source of laws binding power.
Hart held that there is no necessary relationship between a legal system and the ideas of justice or morality. A legal system can function effectively though it is neither just nor moral. The Nazi regime would be a good example of this point.
Hart argues that the question of what is law must be separated from the question of whether it is moral or just. Where as Fuller (Natural Law theorist) maintains that law and morality cannot be so neatly distinguished and that the post-war courts were entitled to hold Nazi rules not to be law. To call the Nazi system legal and to call its rules laws was a false description of what they were. They were instruments of an arbitrary and tyrannical regime.