https://www.salon.com/2017/09/28/are-puerto-ricans-really-american-citizens_partner-2/
Are Puerto Ricans constitutional citizens?
Supreme Court Justice Edward D. White attempted to answer this question when he wrote a concurring opinion in Downes v. Bidwell. His opinion is regarded by scholars as the source of the doctrine on territorial incorporation.
The prevailing consensus to this day is in line with White’s interpretation – that the Citizenship Clause of the 14th Amendment does not extend to Puerto Rico. Since the Downes ruling, for 116 years, Congress has governed Puerto Rico as a separate and unequal territory.
The Jones Act of 1917 included a collective citizenship provision. [P]ersons subsequently born on the island were considered U.S. citizens by way of “jus sanguinis” (blood right), a derivative form of U.S. citizenship. In other words, persons born in Puerto Rico were born outside of the United States but still considered U.S. citizens.
It wasn’t until 1940 that Congress enacted legislation conferring birthright, or “jus soli,” (right of soil) citizenship on persons born in Puerto Rico. The Nationality Act of 1940 established that Puerto Rico was a part of the United States for citizenship purposes. Since Jan. 13, 1941, birth in Puerto Rico amounts to birth in the United States for citizenship purposes.
However, the prevailing consensus among scholars, lawmakers and policymakers is that Puerto Ricans are not entitled to a constitutional citizenship status. While Puerto Ricans are officially U.S. citizens, the territory remains unincorporated. This contradiction has enabled the governance of Puerto Rico as a separate and unequal territory that belongs to, but is not a part of, the United States.
On June 11, Puerto Ricans will vote in a nonbinding status plebiscite deciding whether Puerto Rico should become a state or a sovereign country. If a majority votes for statehood, the question is whether Congress will grant 3.5 million U.S. citizens the ability to live in the 51st state.