Substantive due process.
By the middle of the 19th century, "due process of law" was interpreted by the U.S. Supreme Court to mean that "it was not left to the legislative power to enact any process which might be devised. The due process article is a restraint on the legislative as well as on the executive and judicial powers of the government, and cannot be so construed as to leave Congress free to make any process 'due process of law' by its mere will."
The term "substantive due process" (SDP) is commonly used in two ways: first to identify a particular line of case law, and second to signify a particular attitude toward judicial review under the Due Process Clause. The term "substantive due process" began to take form in 1930s legal casebooks as a categorical distinction of selected due process cases, and by 1950 had been mentioned twice in Supreme Court opinions. SDP involves liberty-based due process challenges which seek certain outcomes instead of merely contesting procedures and their effects; in such cases, the Supreme Court recognizes a constitutionally-based "liberty" which then renders laws seeking to limit said "liberty" either unenforceable or limited in scope. Critics of SDP decisions typically assert that those liberties ought to be left to the more politically accountable branches of government.
Courts have viewed the due process clause, and sometimes other clauses of the Constitution, as embracing those fundamental rights that are "implicit in the concept of ordered liberty". Just what those rights are is not always clear, nor is the Supreme Court's authority to enforce such unenumerated rights clear. Some of those rights have long histories or "are deeply rooted" in American society.
The courts have largely abandoned the Lochner era approach (1897 thru 1937) when substantive due process was used to strike down minimum wage and labor laws in order to protect freedom of contract. Since then, the Supreme Court has decided that numerous other freedoms that do not appear in the plain text of the Constitution are nevertheless protected by the Constitution. If these rights were not protected by the federal courts' doctrine of substantive due process, they could nevertheless be protected in other ways; for example, it is possible that some of these rights could be protected by other provisions of the state or federal constitutions, and alternatively they could be protected by legislatures.
The Court focuses on three types of rights under substantive due process in the Fourteenth Amendment, which originated in United States v Carolene Products Company (1938). Those three types of rights are:
the first eight amendments in the Bill of Rights (for example, the Eighth Amendment);
restrictions on the political process (for example, the rights of voting, association, and free speech); and,
the rights of "discrete and insular minorities".
