"I conclude that Mr. Gallup should be and is hereby disqualified to vote until such time as he is able to prove that he is a citizen of the United States," Hiraga wrote.

The Canadian-born Gallup said he has U.S. citizenship.

"I've maintained that I'm a Native American and that I am a citizen of this country and I have the right to vote," he said.

Gallup, 40, said he planned to appeal the decision. He has 10 days to appeal to the Maui Board of Registration.

The county's investigation was launched after Kihei retiree Steve Riford filed a formal challenge to Gallup's eligibility on Sept. 20.

The Hawai'i Republican Party later sued to have Gallup removed as a candidate. But the Hawai'i Supreme Court threw out the case, saying the GOP didn't followed correct procedure by going directly to the court rather than filing a challenge with the county clerk.

In his written arguments to the clerk, Gallup said he was a citizen, based on his ancestry. His mother is from the Cree tribe, and Gallup said her ancestors had claims to dual citizenship under the Jay Treaty of 1794. The treaty gives Canadian-born Native Americans the right to live and work in the United States and also states that anyone living within U.S. borders for at least one year after the end of the Revolutionary War was to be considered a citizen, Gallup said.