DES MOINES — Gay marriage advocates began celebrating early Friday after the Iowa Supreme Court issued a unanimous ruling finding that the state’s same-sex marriage ban violates the constitutional rights of gay and lesbian couples.

In its decision, the court upholds a 2007 Polk County District Court judge’s ruling that the law violates the Iowa Constitution. It strikes the language from Iowa code limiting marriage to between a man and a woman, making Iowa the third state in the nation where same-sex marriage will be legal.

“We have a constitutional duty to ensure equal protection of the law. Faithfulness to that duty requires us to hold Iowa’s marriage statute … violates the Iowa Constitution. To decide otherwise would be an abdication of our constitutional duty,” the court wrote in its decision.

Court rules dictate that it will take about 21 days for the ruling to be considered final and a request for a rehearing could be filed within that period. That means it will be at least several weeks before gay and lesbian couples can seek marriage licenses.

Polk County Attorney John Sarcone said shortly after the ruling that the county attorney’s office will not ask for a rehearing, meaning the court’s decision should take effect after that three-week period.

“Our Supreme Court has decided it, and they make the decision as to what the law is and we follow Supreme Court decisions,” Sarcone said. “This is not a personal thing. We have an obligation to the law to defend the recorder, and that’s what we do.”

The case has been working its way through Iowa’s court system since 2005 when Lambda Legal, a New York-based gay rights organization, filed a lawsuit on behalf of six gay and lesbian Iowa couples who were denied marriage licenses. Some of their children are also listed as plaintiffs.

The suit named then-Polk County recorder and registrar Timothy Brien.

Des Moines attorney Dennis Johnson, who argued on behalf of the gay and lesbian couples, said “this is a great day for civil rights in Iowa.”

“We have all of you courageous plaintiffs to thank: Go get married, live happily ever after, live the American dream,” he said.

After awaiting the decision at a verdict party in the Des Moines suburb of Urbandale, Laura Fefchak and her partner of 13 years Nancy Robinson were ecstatic.

“Iowa is about justice, and that’s what happened here today,” Fefchak said.

Robinson added: “To tell the truth, I didn’t think I’d see this day.”

Bryan English, spokesman for the Iowa Family Policy Center, a conservative group that opposes same-sex marriage, said many Iowans are disappointed with the ruling and don’t want the courts to decide the issue.

“I would say the mood is one of mourning right now in a lot of ways, and yet the first thing we did after internalizing the decision was to walk across the street and begin the process of lobbying our legislators to let the people of Iowa vote,” English said. “This is an issue that will define (lawmakers’) leadership. This is not a side issue.”

The Rev. Keith Ratliff Sr., pastor at the Maple Street Baptist Church in Des Moines, went to the Supreme Court building to hear of the decision.

“It’s a perversion and it opens the door to more perversions,” Ratliff said. “What’s next?”

Some Iowa politicians began weighing in on the ruling.

Iowa Gov. Chet Culver, a Democrat, said the decision addresses a complicated and emotional issue.

“The next responsible step is to thoroughly review this decision, which I am doing with my legal counsel and the attorney general, before reacting to what it means for Iowa,” Culver said in a statement

U.S. Rep. Leonard Boswell, a Democrat whose district includes Polk County, said he respects the Iowa Supreme Court’s decision.

“I remain consistent in my belief that this is a decision best suited for the states,” Boswell said. “I respect the decision of the court.”

In its unanimous ruling, the Iowa Supreme Court upheld an August 2007 decision by Polk County District Court Judge Robert Hanson who found that a state law allowing marriage only between a man and a woman violates the constitutional rights of equal protection.

The Polk County attorney’s office, arguing on behalf of Brien, claimed that Hanson’s ruling violates the separation of powers and said the issue should be left to the Legislature.

Around the nation, only Massachusetts and Connecticut permit same-sex marriage. California, which briefly allowed gay marriage before a voter initiative in November repealed it, allows domestic partnerships.

New Jersey, New Hampshire and Vermont also offer civil unions, which provide many of the same rights that come with marriage. New York recognizes same-sex marriages performed elsewhere, and legislators there and in New Jersey are weighing whether to offer marriage. A bill that would legalize same-sex marriage in Vermont has cleared the Legislature but may be vetoed by the governor.

The ruling in Iowa’s same-sex marriage case came more quickly than many observers had anticipated, with some speculating after oral arguments that it could take a year or more for a decision.

Richard Socarides, an attorney and former senior adviser on gay rights to President Clinton, said the ruling carries extra significance coming from Iowa.

“It’s a big win because, coming from Iowa, it represents the mainstreaming of gay marriage. And it shows that despite attempts stop gay marriage through right wing ballot initiatives, like in California, the courts will continue to support the case for equal rights for gays,” he said.