Substantive due process
Substantive due process is the idea that the due process clause of the Fourteenth Amendment regulates not only the procedures due a citizen, before revoking a right, but also what rights may be revoked at all. It has become a legal theory tied uniquely in the area of fundamental rights jurisprudence - or, the protection of certain inalienable, yet undefined constitutional rights. Antonin Scalia sharply dissents from almost all cases upholding substantive due process, believing that there are no fundamental rights if they are not defined by the constitution, or discoverable from American history.
Lochner Era, and Before
Ironically, given that substantive due process would later become a tool of liberal jurists, the doctrine began in conservative, and extremely regressive, decisions. The justly reviled decision Scott v. Sanford was the first to suggest that the Constitution protects certain rights (free use of "property," in this case) from intrusion by the government, even if constitutional safeguards had led to a procedurally "correct" taking.[1] Although Dred Scott was thankfully overturned by the Reconstruction Amendments, the seeds of substantive due process were sown in the constitutional landscape.
The doctrine was later, famously, picked up by the Court in Lochner, a decision which held that federal minimum wage laws intruded too far into the "fundamental right" for an employee and an employer to freely contract. This fundamental right could not be abridged even by fair legislative processes. This line of jurisprudence - which came to be known as "economic" substantive due process - came to an abrupt end in the wake of the Great Depression, which forced a nationwide crisis of conscience in the doctrines of full and free laissez-faire, the philosophical underpinnings of Lochner.[2] It was fully overturned in West Coast Hotel.[3]