Balzac v. Porto Rico, 258 U.S. 298 (1922), was a case in which the Supreme Court of the United States held that certain provisions of the U.S. Constitution did not apply to territories not incorporated into the union.

These two per curiam decisions cited the earlier Insular Cases and held that provisions of the Bill of Rights were inapplicable to Puerto Rico even after the passage of the Jones Act.

Although Puerto Rico had been under the control of the United States since the end of the Spanish–American War in 1898, the territory had not been designated for ultimate statehood, and Congress could determine which parts of the Constitution would apply.

He argued that because Puerto Rico had been governed by Spanish civil law for four hundred years before American acquisition, the inhabitants would be unprepared for jury service.

Taft argued that locals should be able to determine their own laws: Congress has thought that a people like the Filipinos, or the Porto Ricans, trained to a complete judicial system which knows no juries, living in compact and ancient communities, with definitely formed customs and political conceptions, should be permitted themselves to determine how far they wish to adopt this institution of Anglo-Saxon origin, and when.Toward the end of the opinion, the court uses "language that would lead to perpetual litigation in an effort to clarify the rights of the American citizens of Puerto Rico":[2] The guaranties of certain fundamental personal rights declared in the Constitution, as, for instance, that no person could be deprived of life, liberty, or property without due process of law, had from the beginning full application in the Philippines and Porto Rico, and, as this guaranty is one of the must fruitful in causing litigation in our own country, provision was naturally made for similar controversy in Porto Rico.The court leaves unresolved the exact "personal rights" that were so "fundamental" that they would extend to American citizens in Puerto Rico.