Law is not a set of given data, conventions or physical facts, but what lawyers aim to construct or obtain in their practice. This marks a first difference between interpretivism and legal positivism. But the refusal that law be a set of given entities opposes interpretivism to natural law too.
There is no separation between law and morality, although there are differences. This is not in accordance with the main claim of legal positivism.
Law is not immanent in nature nor do legal values and principles exist independently and outside of the legal practice itself. This is the opposite of the main claim of natural law theory.