WASHINGTON – Marking a major civil rights turning point, the U.S. Supreme Court on Wednesday struck down Section 3 of the Defense of Marriage Act and paved the way for equal treatment under federal law of legally married same-sex couples.

Read briefs in the case and a transcript of the oral argument.

Justice Anthony Kennedy, writing for a 5-4 majority, said the 1996 law, which defined marriage for federal purposes as between one man and one woman, was a violation of constitutional principles of due process and equal protection of the laws.

"DOMA instructs all federal officials, and indeed all persons with whom same-sex couples interact, including their own children, that their marriage is less worthy than the marriages of others," Kennedy wrote. "The federal statute is invalid, for no legitimate purpose overcomes the purpose and effect to disparage and to injure those whom the State, by its marriage laws, sought to protect in personhood and dignity."

By singling out such marriages as different, Kennedy said the law "humiliates tens of thousands of children" being raised by same-sex couples.

The decision in United States v. Windsor, 12-307, was announced during the final sitting of the high court term, along with another much-awaited ruling on same-sex marriage. In that decision, Hollingsworth v. Perry, 12-144, the justices sidestepped, on jurisdictional grounds, the constitutionality of Proposition 8, the California ballot initiative banning same-sex marriage.

The court did not declare a broad right to same-sex marriage, and the Proposition 8 decision leaves in place laws against same-sex marriage in many states. But civil rights advocates applauded the decision as an important legal step and a sign of rapidly changing views about the rights of homosexuals.

"The Court has rightly told the federal government that it must stand aside and recognize the equal dignity of all marriages conferred by the states. The Windsor opinion continues to expand the liberty and equality rights established by Lawrence v. Texas 10 years ago," said Ruth Harlow, a partner at Pepper Hamilton and an early gay-rights strategist.

"This is truly a day for the history books, one that will be marked by future generations as a giant step forward along our nation's continuing path toward equality," said Roberta Kaplan of Paul, Weiss, Rifkind, Wharton & Garrison, who argued against DOMA at the Supreme Court. "The days of 'skim milk' or second-class marriages for gay people are now over."

James Esseks of the American Civil Liberties Union, who teamed up with Kaplan to argue Windsor, said after a rally at the LGBT Community Center in New York, that the momentum is now with gay marriage.

Unlike the Second Circuit's decision in Windsor (NYLJ, Oct. 19, 3012), which said §3 was unconstitutional after finding that the classification excluding gay and lesbian couples should be subjected to a heightened scrutiny equal protection analysis, Esseks said the Supreme Court "didn't need to get to heightened scrutiny" because the animus shown by Congress "was so clearly unconstitutional."

The decision, Esseks said, "means that the Second Circuit's decision is still good law and that's almost as big a deal as winning at the Supreme Court."

The next step, he said, is working state-by-state on marriage laws. Three states, New Jersey, Illinois and Hawaii have civil unions statutes, and "with the demise of DOMA…all of a sudden there's a big difference between what you get with a civil union and what you get with a marriage. That's going to change."

The decision also underscored the key role of Kennedy, not only as the court's swing vote, but as the author of three pivotal rulings that have advanced gay rights: Romer v. Evans in 1996, Lawrence in 2003, and now Windsor.

"If Bill Clinton was 'the first black president,' Anthony Kennedy has now firmly secured his place in history as 'the first gay justice,'" said Michael Dorf, a professor at Cornell Law School and a former Kennedy clerk.

History, Dorf added, will regard Kennedy as playing the same role for gay rights that Chief Justice Earl Warren did for racial equality.

Within minutes of the decision, President Barack Obama directed Attorney General Eric Holder to work with other executive agencies to review the hundreds of federal statutes that may be affected by the ruling, with an eye toward implementing it "swiftly and smoothly."

Obama also said that the law struck down by the court was "discrimination enshrined in law. It treated loving, committed gay and lesbian couples as a separate and lesser class of people. The Supreme Court has righted that wrong, and our country is better off for it."

Lawyers said the ruling raises a host of issues for private employers who will have to take a fresh look at health and retirement benefits in light of altered federal regulations, even in states that don't permit same-sex marriage.

"Employers should expect that employees will immediately start asking questions about their rights with regard to various employee benefits," said Proskauer Rose senior counsel Roberta Chevlowe.

Complications also will arise because some federal statutes look to where the marriage took place while others are pegged to the state of current residence.

"We're going to be sorting through cross-border issues for months to come," said Scott Squillace, a Boston estates lawyer who advises numerous married gay couples. "In states where same-sex marriage is allowed, they will be capital-M married, but in states that don't allow it, stay tuned."

Squillace also predicted that the decision will prompt many gay couples to get married in states where gay marriage is legal in order to "preserve their rights" under federal law.

Just hours after the decision, Lambda Legal posted a guide to the implications of the ruling for benefits, taxes and immigration, among other legal issues.

It was a tax issue that triggered the lawsuit decided Wednesday by the court. When her spouse Thea Spyer died, plaintiff Edith Windsor had to pay a steep estate tax on what Spyer left to her—a tax that is not imposed on opposite-sex couples. She sued, challenging the constitutionality of DOMA. Windsor won at the district court and at the U.S. Court of Appeals for the Second Circuit. While the case was pending, the Obama administration announced it would no longer enforce that part of DOMA, though it did not give her the tax refund she sought.

In addition to the myriad legal changes the Windsor case will bring, the decision could encourage challenges to state laws banning same-sex marriage.

In dissent, Justice Antonin Scalia angrily said, "By formally declaring anyone opposed to same-sex marriage an enemy of human decency, the majority arms well every challenger to a state law restricting marriage to its traditional definition." Scalia went so far as to reproduce excerpts from the court's opinion with DOMA crossed out and references to state law substituted.

Mayer Brown partner Andrew Pincus said Scalia was correct in his warning. Even though the ruling focuses on the federal law, Pincus said, "there is language in the opinion that reaches more broadly, recognizing that same-sex couples and their children have a strong interest in being allowed the same opportunity as others to enter into relationships recognized by law. That language will be used in future cases to support constitutional challenges to denial of same-sex marriage—as Justice Scalia predicts."

Scalia, who summarized his dissent from the bench, said the court had made a grievous error.

"This case is about…the power of our people to govern themselves, and the power of this Court to pronounce the law," Scalia said. "Today's opinion aggrandizes the latter, with the predictable consequence of diminishing the former. We have no power to decide this case. And even if we did, we have no power under the Constitution to invalidate this democratically adopted legislation."

The court was powerless to act, Scalia said, because both Windsor and the United States were on the same side—with the result that there is no case or controversy for the court to resolve.

"They agree that the court below got it right; and they agreed in the court below that the court below that one got it right as well. What, then, are we doing here?" Scalia asked. Justice Clarence Thomas joined Scalia's dissent.

In a separate dissent, Chief Justice John Roberts Jr. went out of his way, unlike Scalia, to signal that the majority ruling could not be used to keep states from defining marriage as between one man and one woman.

"The Court does not have before it, and the logic of its opinion does not decide, the distinct question whether the States, in the exercise of their 'historic and essential authority to define the marital relation,' may continue to utilize the traditional definition of marriage."

In a third dissent, Justice Samuel Alito Jr. said DOMA was a constitutional expression of the will of the people.

"The Constitution," Alito said, "leaves the choice to the people, acting through their elected representatives at both the federal and state levels."