To those of you who think that all law is mere convention, consider engaging Tim Sandefur’s well-presented defense of the Substantive Due Process doctrine over at Cato Unbound. Here’s Tim’s response to Larry Rosenthal (my First Amendment professor at Chapman Law):
A self-contradiction is nothing; it is null; it is no more a law than it is a pigeon or a sneeze, and a court is therefore justified in disregarding it, even if passed with full procedural formalities. Yet nothing in the Constitution expressly forbids self-contradictory statutes. This prohibition is implicit–embedded in the logic of law itself. As the framers were aware, Francis Bacon made the same point when explaining that a legislature cannot create an unrepealable law (perpetua lex est nullam legem). Nothing in the Constitution expressly forbids unrepealable statutes. Yet such things are prohibited by what Bacon called their “impertinency,” or by what Hamilton called “the nature and reason of the thing.” There are limits on legislative authority imposed by the logic of law itself. That’s why even Blackstone, who believed that government possessed “supreme, irresistible, absolute authority” still admitted it could not do something that is “naturally impossible.” To make an arbitrary, ipse dixit, unauthorized use of force into a “law” is naturally impossible.
If one concedes this much, then one must admit that mere promulgation is not sufficient to make something a “law.” Instead, the legal status of a promulgated rule must be determined at least in part by its content. That is, by its substance: we must ask what a law is, and determine whether something containing the substantive provisions in question meets that definition. That just is substantive due process of law.
A constitution does not tell us what a right is, what a law is, or how to reason. A constitution will be utterly meaningless to a people who either cannot or will not admit these basic notions as inhering in its very idea.