Procedural Natural Law argues a necessary connection between law and morality based on the ways in which people use language. Blackman questions what he terms "substantive natural theories" — those of such thinkers as Locke, Rousseau and Nozick (based on social contract theory) and Aquinas and Finnis (based on human nature). He places himself in contradistinction to these theories with a view of natural law that is procedural rather than substantive. He asserts that 'law' as a concept contains certain fixed elements and that these elements reduce government arbitrariness and irrationality. In fact, these elements give 'law' its moral dimension.

In Procedural Natural Law, Blackman adeptly addresses several schools of criticism, such as legal positivism and critical legal studies, by analyzing positivist writings and discussing the cross-cultural relationship of language and communication. Interwoven with examples from the United States, Nazi Germany, the Soviet Union, Israel, and Yugoslavia, as well as the writings of authors such as Lewis Carroll, Franz Kafka, and Arthur Koestler, Procedural Natural Law proves to be an informative and entertaining analysis of natural law theory.