Who gets to be a U.S. citizen at birth? This question is fairly simple when asked almost anywhere in the United States. If you are born on U.S. soil and you are not the son or daughter of a foreign diplomat stationed here at the time, you are a citizen of this country. The Supreme Court is now considering a case that would require it to decide whether that rule should apply in the only part of the U.S. where it currently does not: the islands of American Samoa.

The case, Fitisemanu v. United States, involves three plaintiffs who originally hail from American Samoa but now reside in Utah. (The petition for review was filed in April; the Department of Justice filed its reply briefs at the end of August.) They are legally considered U.S. nationals, a subcitizenship status of sorts where they still owe allegiance to the U.S. but, unlike Americans on the mainland and in all other territories, did not receive citizenship at birth. This distinction has limited their lives in myriad ways. The case’s namesake, John Fitisemanu, is suing because he cannot lawfully cast a ballot, according to the petition for review. Co-complainant Pale Tuli cannot pursue his preferred vocation as a police officer because Utah law restricts the job to U.S. citizens. And the third plaintiff, Rosavita Tuli, cannot sponsor her parents through the immigration process in the manner to which citizens of the U.S. are entitled.

American Samoa is unique in this regard. Congress has granted birthright citizenship to everyone born in the other U.S. territories—ranging from Puerto Rico and Guam to the U.S. Virgin Islands and Northern Mariana Islands—through federal legislation. While there have been legislative attempts to close this gap, these have met some resistance from local authorities. Both the American Samoan government and the territory’s only congressional delegate moved to intervene in the lawsuit. They argued that imposing birthright citizenship would infringe upon the island’s cultural traditions and right to self-determination.

A federal district court judge ruled in favor of the plaintiffs, however, drawing upon the 1898 case Wong Kim Ark v. United States. That landmark decision helped establish that anyone born on U.S. soil, with the exceedingly rare exception of children of foreign diplomats, automatically acquired U.S. citizenship at birth. The Tenth Circuit Court of Appeals overturned the district court’s ruling in a split decision, concluding that the lower court had applied the wrong set of precedents to the case.

“Between these competing frameworks, the Insular Cases provide the more relevant, workable, and, as applied here, just standard,” Judge Carlos Lucero wrote. “This is so for several reasons: 1) the Insular Cases were written with the type of issue presented by this case in mind, whereas Wong Kim Ark was not; 2) the district court overread the weight accorded English common law by Wong Kim Ark; and 3) the Insular Cases permit this court to respect the wishes of the American Samoan people, whereas Wong Kim Ark would support the imposition of citizenship on unwilling recipients.” Judge Timothy Tymkovich concurred in part, deferring to historical precedent and congressional discretion but declining to apply the Insular Cases outright.

His reticence is understandable. The Insular Cases are among the most controversial precedents that still carry legal weight in American courts. At the close of the nineteenth century, the U.S. acquired a constellation of colonial possessions in the Atlantic and Pacific Oceans by winning the Spanish-American War. Those acquisitions immediately raised questions about when and how the Constitution’s protections applied to the new territories. Did the Constitution follow the flag, so to speak, or could the new possessions be administered under a different type of constitutional order?

In a series of decisions in the early twentieth century, the Supreme Court took the latter approach. Starting with the 1901 case Downes v. Bidwell, the justices distinguished between incorporated territories and unincorporated territories. In incorporated territories, like those on the American frontier that eventually became states, the Constitution carries its full weight. In unincorporated territories, the high court ruled, inhabitants had certain fundamental rights but also did not enjoy the automatic protections of the Bill of Rights or other constitutional measures.

The rulings are widely derided as imperialistic and discriminatory. In some of them, the justices wrote in unabashedly racist terms to muse about whether the nonwhite inhabitants of the new territories were properly suited for “Anglo-Saxon” institutions like jury trials. So condemned are the Insular Cases that the Justice Department under presidents from both parties often disclaims any reliance on them when arguing cases about the territories before the Supreme Court. They nonetheless remain on the books as the prevailing framework for governing the territories where roughly five million people live.