The 5-4 decision leaves Massachusetts as the only state to grant full marriage rights to gay and lesbian couples, and is the latest in a series of significant court rulings in recent weeks to fall in favor of gay marriage opponents.

It also avoids possible widespread challenges of other state's gay marriage restrictions, since Washington -- unlike Massachusetts -- carries no residency restrictions on its marriage licenses.

King County Executive Ron Sims said he is disappointed by the decision.

Sims said he expected a close decision would go the other way. He hopes the next generation of legal minds will recognize homosexual rights to wed.

Sims said his next step is to push for civil unions.

Courts reinstated voter-approved bans on gay marriage in Nebraska and Georgia earlier this month. Tennessee's Supreme Court ruled that voters there should have a say on allowing gay marriage.

Massachusetts' high court -- the same court that issued the historic ruling that has allowed more than 8,000 same-sex couples since 2004 to marry in that state -- ruled a proposed state constitutional amendment to ban gay marriage could go on the ballot if approved by the Legislature.

In Connecticut, a judge found gay and lesbian couples had not been harmed by that state's decision to grant them civil unions but not marriage. Vermont also allows civil unions that confer the same legal rights as heterosexual married couples.

In all, 45 states have passed laws banning gay marriage or limiting marriage to between a man and a woman. Congress recently rebuffed a move to get a constitutional amendment banning same-sex marriage.