UPDATE 1-Gay Marriage Wins Final Legislative Passage in Washington State

* Opponents vow to repeal it at the polls

* Law would not take effect before June 7 (Updates with House vote, details and background)

By Nicole Neroulias

OLYMPIA, Wash., Feb 8 (Reuters) - A bill to legalize gay marriage in Washington state won final legislative approval on Wednesday in a vote that moved the state one step closer to becoming the seventh to recognize same-sex nuptials.

Governor Christine Gregoire, a Democrat in her last term of office, was expected to sign the bill into law early next week, but opponents have vowed to seek its repeal at the polls in November.

The measure cleared the state House of Representatives 55-43, a week after it was passed by the state Senate and a day after a federal appeals court declared California's voter-approved gay marriage ban unconstitutional.

Democrats, accounting for the lion's share of support for the bill, control both legislative bodies in the state capital Olympia but enjoy a bigger majority in the 98-seat House.

Two Republicans joined 53 Democrats in voting for the bill, while two Democrats sided with 41 Republicans in opposition. Senate passage last week came on a 28-21 vote.

Six other states already recognize same-sex marriage -- New York, Massachusetts, Connecticut, Vermont, New Hampshire and Iowa -- as does the District of Columbia.

Supporters are pushing similar statutes in Maryland and New Jersey, and a referendum to legalize gay marriage in Maine has qualified for the November ballot there.

Wednesday's debate grew emotional at times, with the bill's chief House sponsor, Representative Jamie Pedersen, a Democrat who has four young children with his gay companion of 10 years, arguing that the state's domestic-partnership law falls short.

"I would like our four children to understand ... that their daddy and their papa have made that lifelong commitment to each other," he said. "Thousands of same-sex couples in our state deserve the respect and protection from our government that only marriage can convey."

Representative Jay Rodne, a Republican who said he was guided by his Roman Catholic faith to oppose gay marriage, said the measure was tantamount to "progressive re-engineering in its most extreme and damaging form.

"This bill is about validation. This bill is about acceptance ... . Marriage is not about self-actualization, validation or acceptance," he said. "Marriage is about life."

But his Republican colleague, Glenn Anderson, spoke in favor of the bill, referring to his gay brother and drawing a parallel between Jim Crow racial segregation laws in Alabama, where he grew up, and contemporary laws barring same-sex marriage.

BALLOT MEASURES

The bill is to be formally delivered to Gregoire's desk by the end of the week. She will then have five days to sign it, not including Sunday. That timetable has led to speculation of enactment coming next Tuesday, Valentine's Day.

But the law would not take effect before June 7, three months after the conclusion of the legislative session.

Opponents of same-sex marriage said they would seek to overturn the legislation via one of two ballot measures - a referendum for repeal or an initiative defining marriage as the exclusive domain of heterosexual couples.

The former would need 241,153 signatures of registered voters by July 6 to secure a place on the November ballot. The latter would need just half the number of signatures by June 6.

If a repeal referendum qualifies for the November ballot, the gay marriage law would be suspended until the election and certification of returns, meaning Dec. 6, before it is either repealed or goes into effect.

But should gay marriage opponents pursue an initiative, gay marriages could take place on June 7, regardless of ballot-qualification efforts.

It was unclear whether gay weddings performed in the interim would be nullified if an initiative restricting marriage to male-female unions only were to pass in November.

There is precedent in California for handling such a situation. California's Supreme Court legalized gay marriage in 2008, only for voters to approve a state constitutional amendment banning same-sex matrimony six months later.

The state's high court later upheld the gay marriage ban, known as Proposition 8, but ruled that 18,000 same-sex weddings officiated between May and November 2008 were still legal.

A federal judge later ruled Prop 8 unconstitutional, a decision upheld on Tuesday by the 9th U.S. Circuit Court of Appeals.

Legal experts said that ruling, while narrowly tailored to California, could ease the way for a successful court challenge in Washington state should voters there overturn a gay marriage statute. (Writing by Steve Gorman; Editing by Cynthia Johnston and Xavier Briand)