SALT LAKE CITY — A federal judge struck down Utah’s same-sex marriage ban Friday in a decision that marks a drastic shift toward gay marriage in a conservative state where the Mormon church has long been against it.
The decision set off an immediate frenzy as the clerk in the state’s most populous county began issuing marriage licenses to gay couples while state officials took steps to appeal the ruling and halt the process.
Cheers erupted as the mayor of Salt Lake City led one of the state’s first gay wedding ceremonies in an office building about three miles from the headquarters of the Mormon church. Dozens of other couples were lined up to get marriage licenses.
Deputy Salt Lake County Clerk Dahnelle Burton-Lee said the district attorney authorized her office to begin issuing the licenses but she couldn’t immediately say how many had been issued.
Just hours earlier, U.S. District Judge Robert J. Shelby issued a 53-page ruling saying the constitutional amendment Utah voters approved 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.
The decision drew a swift and angry reaction from Utah leaders, including Republican Gov. Gary Herbert.
‘‘I am very disappointed an activist federal judge is attempting to override the will of the people of Utah. 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,’’ Herbert said.
The state filed a notice of appeal late Friday and was working on a request for an emergency stay that would stop marriage licenses from being issued to same-sex couples.
‘‘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. Bruckman said the judge told the attorney general’s office that it would be a couple of days before he would review any request for an emergency stay.
The ruling has thrust the judge into the national spotlight less than two years after Congress approved his nomination to the federal bench. Shelby was appointed by President Barack Obama after GOP Sen. Orrin Hatch recommended him in November 2011.
Shelby served in the Utah Army National Guard from 1988 to 1996 and was a combat engineer in Operation Desert Storm. He graduated from the University of Virginia law school in 1998 and clerked for the U.S. District Judge J. Thomas Greene in Utah, then spent about 12 years in private practice before he became a judge.
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.
The Utah 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.
If the ruling stands, Utah would become the 18th state to allow gay marriages, said Jon Davidson, director of Lambda Legal, which pursues litigation on LGBT issues nationwide. That’s up from six before the U.S. Supreme Court last summer struck down part of the Defense of Marriage Act that defined marriage as between a man and a woman. The District of Columbia also allows same-sex marriage.
‘‘The momentum we are seeing is unprecedented in any human rights struggle,’’ Davidson said. ‘‘To have this fast a change in the law and in public opinion, is quite remarkable.’’
State Sen. Jim Dabakis, chairman of the Utah Democratic Party, was one of the first to get married in Salt Lake City with his longtime partner, Stephen Justesen.
‘‘Do you, Jim, take Steven, to be your lawfully wedded spouse?’’ the mayor asked during the ceremony, shortly before a celebration erupted.
Marriage ceremonies were being performed once every few minutes in the lobby of the clerk’s office, each one punctuated by hoots and hollers from the large crowd.
Brian Morris let out a loud yelp after getting married to his partner, who dissolved into tears.
‘‘I'm so exicted,’’ Morris yelled. ‘‘I love you.’’
But at the Utah County clerk’s office in Provo, same sex-couples were still denied marriage licenses.
Patsy Carter, 42, and her partner of eight years, 39-year-old Raylynn Marvel, said they went to the office immediately after hearing about the ruling but the clerk said they office was still reviewing the ruling and consulting with the county attorney.
Carter said the ruling was still a positive step and she believes Utah County, considered one of Utah’s most conservative, will eventually have to start granting the licenses.
‘‘If my marriage licenses could say, ‘Provo, Utah,’ that’s probably the most epic contradiction ever,’’ she said.
Utah’s lawsuit was brought by three gay and lesbian couples, including one that was legally married in Iowa and just wants that license recognized in Utah.
One of the couples that brought the case, Moudi Sbeity and Derek Kitchen, were roasting eggplants for a farmers market Saturday when their lawyer, Peggy Tomsic, called them with the 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.’’
During the nearly four-hour hearing on the case, 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 doesn’t give same-sex couples the universal right to marry.
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.
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.
Associated Press writers Paul Foy and Michelle Price contributed to this report.