Gays and civil rights activists exulted Thursday over the Supreme Court's decision striking down the Texas anti-sodomy law, while conservatives said it could lead to same-sex marriage.

Gay-rights activists, who regarded the challenge to the anti-sodomy law (search) as one of their most important legal cases in decades, said the high court's ruling will go far toward guaranteeing equal rights for homosexuals.

"This decision is a historic, transformative decision," said Ruth Harlow, who as legal director of Lambda Legal (search) was the lead attorney in the case. "The court had the courage to reverse one of its gravest mistakes, and to replace that with a resounding statement of equality and liberty for all."

The Supreme Court was criticized by civil rights groups 17 years ago when it upheld a Georgia law similar to Texas'. With its 6-3 decision Thursday, the court majority overturned the Texas anti-sodomy statute and appeared to sweep away laws in a dozen other states that ban oral and anal sex for everyone, or for homosexuals in particular.

Though seldom enforced by police, the laws are sometimes invoked by judges to deny homosexuals legal custody of their children, equal employment guarantees and other rights.

"For years, whenever we have sought equality, we've been answered both in courts of law and in the court of public opinion with the claim that we are not entitled to equality because our love makes us criminals," said James Esseks, litigation director of the American Civil Liberties Union (search)'s Lesbian and Gay Rights Project. "That argument -- which has been a serious block to progress -- is now a dead letter."

Reaction was especially strong in states with sodomy laws: Kansas, Oklahoma, Missouri, Alabama, Florida, Idaho, Louisiana, Mississippi, North Carolina, South Carolina, Texas, Utah and Virginia.

"It could have been a historic day just for Texas, but it's a historic day, period," said Paul Scott, executive director of the Dallas-based John Thomas Gay and Lesbian Community Resource Center.

The president of the Christian Coalition of Alabama, John Giles, said he worries the decision will further a national campaign to legalize marriage between gays.

"God have mercy on America," he said.

Mathew D. Staver, president of Liberty Counsel, an Orlando, Fla.-based religious rights group, predicted that conservatives would not let the court's decision stand unchallenged.

"The split decision underscores the importance of the next Supreme Court appointment, not only on the issue of abortion but now on the issue of same-sex unions," he said. "Regulating homosexual conduct and marriage is the right of the people to be exercised through the legislative rather than judicial branches of government."

The ruling came in a case brought by two men arrested in 1998. They were jailed overnight and ordered to pay $200 in fines after police, responding to a false complaint of an armed intruder, discovered them having sex in their bedroom.

"We never chose to be public figures or to take on the spotlight. We also never thought we could be arrested this way," said one of the men, John Lawrence. "We are glad this ruling not only lets us get on with our lives, but opens the door for all gay people to be treated equally."

That the high court's ruling came in June, the month traditionally reserved for gay pride celebrations across the country, made the victory all the more sweet, advocates said.

Gay advocacy groups from Alaska to Florida planned celebrations later in the day.