The only Supreme Court case in which the Third Amendment did any heavy lifting is Griswold v. Connecticut, a case that’s not about troop-quartering, but about birth control. The Supreme Court held that the Third Amendment’s “penumbra” (a legal term that predates the Griswold case) extended to protecting the privacy of the home from government intrusions. “Would we,” asked the court, “allow the police to search the sacred precincts of marital bedrooms for telltale signs of the use of contraceptives?” The very idea, said the court, was “repulsive.”
Likewise, the U.S. Court of Appeals for the Second Circuit held in Engblom v. Carey that the Third Amendment protects a “fundamental right to privacy” in the home. Since then, courts haven’t done much to flesh these holdings out, but I wonder if they should. In the 18th century, when the Third Amendment was drafted, “troop quartering” meant literally having troops move into your house to live at your expense and sleep in your beds. It destroyed any semblance of domestic privacy, opening up conversations, affection, even spats to the observation and participation of outsiders. It converted a home into an arena.