Oregon's gay marriage ban on Monday was ruled unconstitutional by U.S. District Court Judge Michael McShane.
The judge ordered that state officers are permanently restricted from enforcing the state constitutional amendment banning gay marriage and a separate applicable law.
McShane acknowledged many in the state have moral and religious objections to gay marriage. He said past generations, including his, were raised in a world where "homosexuality was believed to be a moral perversion, a mental disorder, or a mortal sin."
"At the core of the Equal Protection Clause, however, there exists a foundational belief that certain rights should be shielded from the barking crowds; that certain rights are subject to ownership by all and not the stake hold of popular trend or shifting majorities," he wrote in his opinion.
The ruling was widely expected, as the Oregon attorney general declined to defend the law in court after determining that it violated the Constitution. Last week the judge also denied a request from a group opposing gay marriage, the National Organization for Marriage, to step in to defend the law.
Earlier in the day, a U.S court of appeals also denied an emergency stay to halt the ruling.
The case was brought on behalf of four same-sex couples. Some county clerks were expected to begin handing out gay marriage licenses shortly after the ruling.
Oregon approved a gay marriage ban in the state constitution by referendum in 2004 with 57 percent of the vote.
Monday’s decision is just the latest state ruling striking down a gay marriage ban. Arkansas and Idaho earlier this month had their marriage laws struck down pending appeal.
Seventeen states, aside from Oregon and the District of Columbia, allow same-sex marriage. Judges in seven other states have stuck down their state's gay marriage ban, but those decisions are temporarily delayed pending appeal.
A number of others states have also ruled against their states' ban on recognizing gay marriages performed in other states.
The spate of rulings in the past year have come after the Supreme Court struck down a portion of the Defense of Marriage Act that defined marriage as being between a man and a woman.
—Updated 3:45 p.m.