Foreign in a domestic sense

In 1901, the U.S. Supreme Court answered a question that no one had really needed to ask before: does the Constitution apply automatically, completely, to a territory that the United States has just acquired by force?

The answer came through a series of rulings known collectively as the Insular Cases, about the legal status of Puerto Rico, Guam, and the Philippines, all newly acquired in the Spanish-American War. The name comes from the fact that those territories were administered by the Bureau of Insular Affairs of the War Department, a bureaucratic detail that ended up naming an entire body of constitutional law.

The best-known case, Downes v. Bidwell, decided in 1901, is usually summarized with a single dry question: does the Constitution follow the flag? The Court's answer was narrow and weighty. It held that the Constitution does not necessarily apply in full to the territories, and that Congress has broad power to legislate for them in ways that would be unconstitutional in a state, especially in matters of taxation and revenue, exactly the kind of law then shaping Puerto Rico's economy.

That ruling created a legal category that had not existed before: the "unincorporated territory," a status distinct from both statehood and the older path of an incorporated territory toward eventual statehood. It was, in practice, a permanently intermediate status, neither fully inside the constitutional system nor fully outside it.

This was not a one-off technicality confined to 1901. The doctrine established by the Insular Cases still governs the legal status today of Puerto Rico, Guam, American Samoa, the U.S. Virgin Islands, and the Northern Mariana Islands, more than a century later.

That is why 1901 is a strange hinge. A handful of Supreme Court opinions, written for a very particular moment right after the war, ended up defining the edge of what U.S. citizenship and constitutional protection mean for millions of people living in U.S. territories, and that frontier has not been fully redrawn since then.

Sources: Casos Insulares; Downes v. Bidwell. Freeze 2026-08-22.