“It’s been a struggle for so many — they pay their taxes, they do what they’re supposed to do, but they can’t have a job in the police force and do other things because they’re not citizens,” said Susi Lafaele, co-founder of the Southern Utah Pacific Islander Coalition, one of four plaintiffs in the case. “This decision not only gives them the right to vote, but gives that sense of pride of being part of the United States.”

John Fitisemanu, a 54-year-old resident of Woods Cross, Utah, who was the lead plaintiff in the case, said he registered to vote for the first time on Friday morning, just before Judge Waddoups stayed the ruling.

“It’s overwhelming,” said Mr. Fitisemanu, who works at a medical testing company and has lived in Utah for more than 20 years. “But I’m most excited to be able to call myself a citizen of the United States of America at this time. It’s been a long time coming.”

Mr. Fitisemanu had argued in court papers that it was unjust to deny him the same rights as other Americans and that he was distressed that some assumed he was merely choosing not to vote or was a foreigner.

Representative Aumua Amata Coleman Radewagen, a Republican who represents American Samoa in Congress, said she was disappointed in the decision and argued it would “come as a surprise to tens of thousands of American Samoans that a federal judge in Utah has ruled that they are now United States citizens.”

“While there is room for American Samoans to have different opinions about whether to seek United States citizenship, there are deep concerns about having a distant federal judge decide these issues,” Ms. Radewagen said, adding that the decision would be appealed.

Judge Waddoups ruled that American Samoans must be granted citizenship under the 14th Amendment, which was ratified in 1868 to extend citizenship to African-Americans after the abolition of slavery.