In his ruling, 3rd District Judge Keith A. Kelly said that Salt Lake County Clerk Sherrie Swensen "abused her discretion" by denying a voter challenge from Alta resident Guy Jordan in 2010.
Jordan challenged Gilman's right to vote in Alta, alleging that the veteran ski patroller lives in Cottonwood Heights with his wife and children. Jordan produced a deed of trust to Gilman's Cottonwood Heights house as evidence.
Kelly ruled in part: "The county clerk was not sure of the legal analysis supporting her decision or the basis for the decision that Jordan had failed to meet his burden of proof in his voter challenge."
The judge ordered Jordan's voter challenge to be implemented, but the time frame for such action remained unclear Monday.
In a short telephone interview Monday, Gilman said he and his attorney have not yet decided whether to appeal Kelly's decision. If he were to appeal, he would retain his seat until the matter is fully adjudicated.
If he doesn't appeal and steps aside, the council would appoint someone to complete his term, which runs through 2015, said Town Manager John Guldner.
Swensen, too, could appeal the ruling because Jordan brought the case against the county clerk, according to Gilman. "I was just attached to it," he said.
Swensen could not be reached for comment Monday.
Most people who work in Alta cannot afford housing there, Gilman said.
"The problem I see, if this is the law, many people who have invested their lives in Alta will be disenfranchised," Gilman said. "You can spend a couple of years in company housing, but eventually everybody needs a place of their own."
Gilman, who began working for the ski resort in 1979, is in his third term on the council. His most recent election victory in November 2011 was determined by a coin toss after he and challenger Merebea Danforth each got 60 votes.
According to county records, 215 people are registered to vote in Alta.
Kelly's ruling served justice, according to Jordan, who does own a home in Alta.
"The court interpreted the law and set a new standard," Jordan said Monday. "I have nothing personal against Gilman. This is about a strong belief in the right to vote and the right to vote where you live."
It is the first challenge under a statute passed in 2010 that allows Utahns to appeal a county clerk's decision on voter eligibility. Prior to that, the clerk's decision was final.
The Town Council should represent all interests, Jordan said.
"The Town Council has to take a balanced approach to Alta the ski area, the businesses and the residents," he said. "This is a town, not just a ski area."