In the Balzac v. People of Porto Rico case in 1921, the U.S Supreme Court ruled that certain provisions of the U.S Constitution did not apply to territories not incorporated into the union. The case involved Jesús M. Balzac who was convicted for libel in a Puerto Rican court without a jury trial, which he argued violated his Sixth Amendment rights to a fair trial by jury as an American citizen after Puerto Rico became a territory of United States under Jones Act (1917). However, the Supreme Court held that while Congress had granted citizenship to people born in Puerto Rico through this act, it hadn't indicated intent to incorporate it as part of Union and therefore full constitutional rights were not extended there unless explicitly stated by Congress. This decision established "the doctrine of territorial incorporation", where only fundamental constitutional rights are guaranteed in unincorporated territories like Puerto Rico.

In the dissenting opinion for Balzac v. People of Porto Rico, Justice John H. Clarke argued that Puerto Ricans should be granted full constitutional rights as American citizens. He disagreed with the majority's interpretation of the Insular Cases and believed they were wrongly decided, asserting that once a territory has been incorporated into the United States, its inhabitants automatically become U.S. citizens entitled to all constitutional protections regardless of their location or status as a territory rather than a state. He criticized his colleagues' decision for creating an unjust distinction between different types of American territories and depriving Puerto Ricans of their fundamental rights under the Constitution despite being recognized as U.S citizens by Congress in 1917 through Jones Act.