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Despite Donald Trump’s periodic threats to terminate birthright citizenship, it remains the law of the land—except for one small territory. The federal government designates individuals born in American Samoa as “noncitizen nationals,” which denies them a fundamental right granted to those born anywhere else in the country. On Thursday, however, U.S. District Judge Clark Waddoups ruled this practice unconstitutional, directing the government to recognize the citizenship of individuals born in American Samoa. (More than 55,000 people live on the island, most of whom were born there.) Waddoups’ decision is the first volley in a fight that may force the Supreme Court to assess the scope of birthright citizenship for the first time in more than a century.

The right to American citizenship has long expanded and contracted along racial lines, and it is no coincidence the last remaining class of Americans denied citizenship are nonwhite. After the American Revolution, the nation followed the English rule extending citizenship to anyone born within the country, including its territories. But in 1857’s notorious Dred Scott v. Sandford, the Supreme Court abolished this principle, ruling that black people could not become American citizens. The 14th Amendment was intended in part to reverse Dred Scott and restore birthright citizenship. Its very first sentence states: “All persons born or naturalized in the United States and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside.”

In 1898’s U.S. v. Wong Kim Ark, the Supreme Court confirmed that this provision guarantees citizenship to individuals born in America, including the children of immigrants. But that same year, the U.S. was launching a foray into imperialism that would bring new, far-flung territories under its control. Previous territories in the continental U.S. had been considered destined for statehood once they filled up with white settlers. But these new territories—like American Samoa, ceded to the U.S. in 1900—were acquired for essentially defensive purposes, not to create eventual new states.

In a series of rulings in the early 20th century known as the Insular Cases, the Supreme Court ruled that the Constitution did not apply fully in these new possessions. The court deemed this new territories “unincorporated”—that is, not on the path to statehood. Because unincorporated territories were “inhabited by alien races,” the court reasoned, governing them “according to Anglo-Saxon principles may for a time be impossible.” Thus, only “fundamental” constitutional rights applied. Is birthright citizenship a “fundamental” right? Several justices implied that it might not be in 1901’s Downes v. Bidwell. Yet a majority of the Supreme Court has never squarely held that individuals born in unincorporated territories may be denied American citizenship.

In the following decades, Congress extended birthright citizenship to the nation’s other territories. But it never did so for American Samoa. Today, individuals born on the island receive a passport that says: “THE BEARER IS A UNITED STATES NATIONAL AND NOT A UNITED STATES CITIZEN.” If they move to a state, they are not permitted to vote in elections or work in many government jobs because of their noncitizen status. American Samoa has the highest rate of military enlistment of any U.S. state or territory, yet American Samoans are barred from certain positions in the armed forces because they aren’t citizens. They are the last remaining caste of Americans who receive formal second-class citizenship.

They are the last remaining caste of Americans who receive formal second-class citizenship.

Frustrated by this predicament, three American Samoans living in Utah, along with the Southern Utah Pacific Islander Coalition, filed a lawsuit alleging that the government is violating the 14th Amendment by denying them birthright citizenship. (The plaintiffs are represented by the advocacy group Equally American, which fights for territorial rights.) And on Thursday, Waddoups, a George W. Bush appointee, ruled in their favor. His meticulous 69-page opinion begins with a lengthy exploration of the 14th Amendment’s text and history, both of which suggest that its framers intended it to apply to states and territories. For instance, Sen. Lyman Trumbell, who helped craft the amendment, declared that it “refers to persons everywhere, whether in the States or in the territories or in the District of Columbia.” (Emphasis added.)

In the end, Waddoups concluded that Wong Kim Ark controls this case. The Supreme Court has never overruled (or even questioned) Wong Kim Ark, and the Insular Cases never expressly carved out an exception for territories. American Samoans are therefore “citizens by virtue of the Citizenship Clause of the Fourteenth Amendment,” and “Congress has no authority to deny them citizenship.” The judge prohibited the government from enforcing any law to the contrary, requiring it to honor the citizenship of those born in American Samoa.

The Department of Justice will appeal Waddoups’ decision to the U.S. Circuit Court of Appeals for the 10th Circuit. The administration’s opposition here cannot be attributed to sheer bigotry. Barack Obama’s Department of Justice took the same position and won in the U.S. Court of Appeals for the District of Columbia Circuit in 2016. (The Supreme Court declined to review the case.) There is a real chance that the 10th Circuit will affirm Waddoups’ careful ruling and follow Wong Kim Ark. That would create a circuit split, all but forcing the Supreme Court to resolve the dispute.

Anti-immigrant activists filed a brief in this case, hoping to use it as a vehicle to end birthright citizenship for undocumented immigrants. But the Supreme Court likely has little desire to reverse long-standing precedent by radically rewriting the 14th Amendment. More plausible is the possibility that the court might erode or overturn the Insular Cases, rooted as they are in explicit racism. At a bare minimum, the justices could acknowledge that the Constitution compels birthright citizenship everywhere in the U.S.—even those territories “inhabited by alien races.”

Is this wishful thinking? With this ultraconservative court, perhaps. But at least the case will force this issue into public consciousness. Far too few Americans know or care about their fellow citizens (or “nationals”) in the country’s overseas territories. A vestige of colonialism, these territories remain trapped in legal limbo, their residents languishing in what one federal judge termed “citizenship apartheid.” And because they have no representation in Washington—no vote in Congress or presidential elections—the courts may be their sole recourse. As Waddoups illustrated on Thursday, the judiciary is perfectly capable of vindicating their rights.