Substantive Due Process and the Right to Privacy

The word privacy never appears in the Constitution, so where does the right come from? Start with due process. Procedural due process asks whether the government followed fair procedures before taking your life, liberty, or property. Substantive due process asks a different question: can this law exist at all, no matter how fairly it is enforced? Some liberties, the theory goes, are so fundamental that no fair procedure can justify invading them. Privacy became one of those liberties.

Griswold v. Connecticut (1965) is the clearest demonstration. Connecticut banned the use of contraceptives, even by married couples. The Court could not point to one amendment that said 'privacy.' Instead it pointed to several: the First Amendment's protection of association, the Third's bar on quartering soldiers in homes, the Fourth's protection against unreasonable searches, the Fifth's protection against self-incrimination. Justice Douglas argued these amendments have penumbras, zones of protection that extend beyond their literal text, and that the penumbras overlap to create a broader zone of privacy. The marriage bedroom fell inside that zone, so the law banning contraceptives could not stand, regardless of how it was enforced.

This is how unenumerated rights get built: a case establishes the right, later cases extend it to new situations, and later Courts can narrow it again without erasing the method itself. Griswold's privacy logic fed into later rulings on contraception access for unmarried people, and on other personal decisions. The same doctrine that expands rights can contract them, which is why this topic sits next to cases about how far substantive due process reaches and where the Court has pulled back.