Complex sentence: Due to their value-free approach, legal realists are opposed to natural law traditions, which traditions they regard as objects of investigation to be historically explained by making use of a variety of psychological and sociological hypotheses.
Split into simpler sentences: Due to their value-free approach, legal realists are opposed to natural law traditions. Legal realists regard these traditions as historical and/or social phenomena to be explained by making use of a variety of psychological and sociological hypotheses.