[T]he conservatives reject substantive due process, which they see as a contradiction in terms that authorizes judges to legislate. If the term sounds odd, it would be odder still to dismiss the idea. As Roger Pilon writes, “By ‘law’ [in due process of law] the drafters could hardly have meant mere legislation or the guarantee would have been all but empty.” In other words, if a legislature may “duly” pass any substantive law it wishes, life, liberty, and property are hardly secure. Substantive due process is an indispensable restraint on legislative caprice.

“Dissolving the Inkblot: Privacy as Property Right,
Cato Policy Report, Jan-Feb 1993