A federal judge on Monday struck down Oregon's ban on gay marriage.

“Because Oregon's marriage laws discriminate on the basis of sexual orientation without a rational relationship to any legitimate government interest, the laws violate the Equal Protection Clause of the Fourteenth Amendment to the United States Constitution,” U.S. District Judge Michael McShane wrote in his 26 page brief.

The ruling comes on the heels of similar decisions in Idaho and Arkansas.

But unlike those states, Oregon's attorney general sided with plaintiffs and urged McShane to strike down the ban.

“We simply can't imagine a rationalization for the ban,” a lawyer for the state told McShane during arguments.

Weddings are expected to begin as early as Monday, provided counties wave a 3-day waiting period.

Thalia Zepatos, director of public engagement at Freedom to Marry and an adviser to Oregon United for Marriage, cheered the ruling.

“Today Judge McShane did the right thing for families, affirming that the denial of marriage to committed same-sex couples in Oregon is unconstitutional,” Zepatos said in a statement. “In recognition of the strong support for marriage among Oregonians, no one with legal standing, including our state Attorney General, wanted to go down in history as defending discrimination. Across the country, the courts agree: same-sex couples and their families need the protections of marriage, and anti-marriage laws are indefensible. With over 70 marriage cases now making their way through the courts, today's decision in Oregon underscores that all of America is ready for the freedom to marry.”

The National Organization for Marriage (NOM) made a last-minute attempt to delay the ruling, filing for an emergency stay with the Ninth Circuit Court of Appeals in San Francisco. The court denied NOM's request.

(Related: Gay marriage foe NOM denied emergency stay in pending Oregon marriage ruling.)