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A federal judge struck down Utah's same-sex marriage ban Friday in a decision that brings an increasing nationwide shift toward allowing gay marriage to a conservative state where the Mormon church has long been against it.

U.S. District Judge Robert J. Shelby issued a 53-page ruling saying Utah's law passed by voters in 2004 violates gay and lesbian couples' rights to due process and equal protection under the 14th Amendment.

Shelby said the state failed to show that allowing same-sex marriages would affect opposite-sex marriages in any way.

"In the absence of such evidence, the State's unsupported fears and speculations are insufficient to justify the State's refusal to dignify the family relationships of its gay and lesbian citizens," Shelby wrote.

Late Friday, the state filed both a notice of appeal of the ruling and a request for an emergency stay that would stop marriage licenses from being issued to same-sex couples. It's unknown when the judge will make a decision on whether to grant the stay.

"It will probably take a little bit of time to get everything in place," said Ryan Bruckman, a spokesman for the attorney general's office. He said the judge told the attorney general's office it would be a couple of days before any request for an emergency stay would be reviewed.

Gov. Gary Herbert vowed to “defend traditional marriage” in light of the ruling.

“I am very disappointed an activist federal judge is attempting to override the will of the people of Utah,” Herbert said in a statement. “I am working with my legal counsel and the acting attorney general to determine the best course to defend traditional marriage within the borders of Utah.”

The Salt Lake County clerk's office started issuing marriage licenses to same-sex couples. Deputy Clerk Dahnelle Burton-Lee said the district attorney authorized her office to begin issuing the licenses but she couldn't immediately say how many have been issued so far.

Utah's lawsuit was brought by three gay and lesbian couples. One of the couples was legally married in Iowa and just wants that license recognized in Utah.

One of those couples, Moudi Sbeity and Derek Kitchen, were roasting eggplants for a farmer's market tomorrow when their lawyer, Peggy Tomsic, called them with the big news.

"We had a positive feeling after the hearing on Dec. 4, but it's still a surprise to hear it," Sbeity said. "We're excited and happy and hopeful to see what happens what next."

The couple, which owns a company that makes Middle Eastern food spreads and sells them to supermarkets, won't be getting married right away. They want to see if the state appeals.

Another of the couples, Laurie Wood and Kody Partridge, said they were elated.

"I'm just kind of in shock. My brother called and said, `When are you getting married?" said Wood, 58, an English professor Utah Valley University.

The ruling comes the same week New Mexico's highest court legalized gay marriage after declaring it unconstitutional to deny marriage licenses to same-sex couples. A new law passed in Hawaii last month now allows gay couples to marry there.

During a nearly four-hour hearing earlier this month in Salt Lake City, attorneys for the state argued that Utah's law promotes the state's interest in "responsible procreation" and the "optimal mode of child-rearing." They also asserted it's not the courts' role to determine how a state defines marriage, and that the U.S. Supreme Court's ruling last summer that struck down part of the Defense of Marriage Act doesn't give same-sex couples the universal right to marry.

Many similar challenges to same-sex marriage bans are pending in other states, but the Utah case has been closely watched because of the state's history of staunch opposition to gay marriage as the home of The Church of Jesus Christ of Latter-day Saints.

The church said in a statement Friday that it stands by its support for "traditional marriage."

"We continue to believe that voters in Utah did the right thing by providing clear direction in the state constitution that marriage should be between a man and a woman, and we are hopeful that this view will be validated by a higher court," the church said.

Tomsic applauded Shelby's courage in making the ruling but warned that the legal fight is not over, saying she expects the state to take the case to the 10th U.S. Circuit Court of Appeals.

During this month's hearing, Tomsic contended marriage is a fundamental right protected by the U.S. Constitution. She said the case embodies the civil rights movement of our time, saying discrimination has gone on long enough.

She said Utah's law, which passed with two-thirds of the vote, is "based on prejudice and bias that is religiously grounded in this state."

In the ruling, Shelby wrote that the right to marry is a fundamental right protected by the U.S. Constitution.

"These rights would be meaningless if the Constitution did not also prevent the government from interfering with the intensely personal choices an individual makes when that person decides to make a solemn commitment to another human being," Shelby wrote.

The Associated Press contributed to this report.