Oxymoron is a figure of speech in which two opposite ideas are joined to create an effect.
This question can be solved in the following way:
The basic theories of the basis of I Law are contradictory.
1. John Austin is of view that I law is based on morality. While other Jurists, like Oppenheim, say that it has legal binding force.
2. Naturalist and positivist theory.
3. Differences on subjects of I law.
In this way, you can interpret this question and give balanced conclusion by taking in view the contradictory theories.