After a lonely six-year battle, retired Air Force officer Arnold Davis, a resident of Guam, has finally won his right to register to vote in the U.S. territory and participate in a plebiscite on its future.

On March 8, Judge Frances Tydingco-Gatewood ruled that Guam’s law limiting registration and voting to “Native Inhabitants” of the island is a violation of the Fourteenth and Fifteenth Amendments. As the judge said, the Constitution does not allow the government “to exclude otherwise qualified voters in participating in an election where public issues are decided simply because those otherwise qualified voters do not have the correct ancestry or bloodline.”

This decision has been a long time coming. The suit, filed by J. Christian Adams and the Center for Individual Rights in 2011, arose when Davis tried to register to vote on the plebiscite. His application was rejected and marked as “void” by the Guam Election Commission because he is white.

Guam, you see, banned residents from registering or voting unless they were Chamorro “natives,” which to the territorial government means people whose ancestors were original inhabitants of Guam. Chamorros constitute only about 36 percent of the island’s present population.

The race-based voting ban clearly violated the Constitution and the Voting Rights Act, yet the Obama Justice Department refused to protect Davis or any of the other disenfranchised residents of the island. It neither filed suit against Guam nor intervened in support of the lawsuit filed by Adams and the Center for Individual Rights. Instead, it gave Guam $300,000 to help finance the plebiscite.

The case itself has a complicated procedural history that included a trip to the Ninth Circuit Court of Appeals, which reversed Tydingco-Gatewood’s original decision dismissing the case. The dismissal was based on erroneous arguments that Davis didn’t have standing to sue and that his claim was not ripe. The Ninth Circuit sent the case back to Tydingco-Gatewood, holding that Davis not only had standing to challenge Guam’s race-based voting law, but that the claim was ripe because Davis was alleging that “he was currently subjected to unlawful unequal treatment in the ongoing registration process.”

In her March 8 decision, Tydingco-Gatewood did what she should have done in the first place: applied the precedent set by the U.S. Supreme Court in Rice v. Cayetano (2000). In Rice, SCOTUS threw out a similar voting restriction enacted by Hawaii, holding that the Fifteenth Amendment “prohibits all provisions denying or abridging the voting franchise of any citizen or class of citizens on the basis of race,” and making clear that ancestry cannot be used as a proxy for race.

Judge Tydingco-Gatewood also noted the Supreme Court’s decision in another infamous case, Hirabayashi v. U.S. (1943). In that case, which concerned the treatment of Japanese Americans during World War II, the Court noted: “Distinctions between citizens solely because of their ancestry are by their very nature odious to a free people whose institutions are founded upon the doctrine of equality.” Judge Tydingco-Gatewood went on to cite specific discussions by territorial legislators that make it very clear that the Guam legislature intended to “manipulate the system to exclude” anyone other than Chamorros from voting — an obvious violation of the Fifteenth Amendment.

Calvo’s defiance makes it all the more essential for the Justice Department to bring its heft to bear against any efforts to subvert the judge’s ruling.

The judge also found that Guam had violated the Fourteenth Amendment by denying equal protection to its residents. All “Guam voters have a direct interest and will be substantially affected by any change to the island’s political status.” Guam had asserted that only the “colonized people” of the island should be allowed to vote on its future political status. But, the judge noted, the island failed to cite any legal authority that would allow it to “disregard or circumvent the U.S. Constitution and the laws of the United States.”

The defiant attitude displayed throughout this litigation by Guam officials and plebiscite activists reared its ugly head again after the ruling came out. Joe Garrido, chairman of the “Free Association Task Force” organized by Guam’s Commission on Decolonization, called Tydingco-Gatewood a “colonized federal judge” who is “not working for the Chamorro people. . . . She is working for the government that is colonizing Guam.”

In his “State of the Island” address, delivered just two days before the decision, Guam governor Eddie Calvo said that if the federal court ruled against Guam, he would “petition the other branches of the federal government to secure the right of our people against this continuing subjugation.” He promised that he would not turn his “back on the Chamorro people,” although he is apparently willing to turn his back on the other 64 percent of island residents who don’t fit his definition of a Guam “native.”

After the ruling, Calvo issued a statement vowing to find a “way to work around” it, adding that when the judge “says we can’t — I say we can.” He even proposed changing the plebiscite by having “two separate boxes — one would be marked if you’re a native inhabitant and the other would be marked if you’re a non-native.”

Calvo’s defiance makes it all the more essential for the Justice Department to bring its heft to bear against any efforts to subvert the judge’s ruling. If the governor actually tries to implement a racially segregated ballot as he has suggested he will, the Justice Department must act.