Substantive Due Process, Penumbras

Patrick asked about substantive due process. A report from the Congressional Research Service has a nice summary:

The Due Process Clauses of the Fifth and Fourteenth Amendments provide that no
person shall be deprived of “life, liberty, or property, without due process of law.” The U.S. Supreme Court has understood due process to protect both procedural and substantive rights. Under the doctrine of substantive due process, the Court has held that certain rights, while not expressly recognized in the text of the Constitution, are subsumed within the notion of liberty in the Due Process Clauses. One aspect of the liberty interest protected by the Due Process Clauses is a right of personal privacy or “a guarantee of certain areas or zones of privacy.” The Court has found that
certain personal rights that can be deemed “fundamental” are included in this guarantee of personal privacy.

The report discussed the idea in the context of cloning, which (surprise!) also has a religious angle.

Here is an outline explanation of Griswold ("penumbras" and "emanations.")