The following editorial appeared recently in The Washington Post.

In 2007, Edith Windsor married Thea Spyer, her partner of 42 years, in Canada. Two years later, Ms. Spyer died. If the New York couple had been been man and woman, Ms. Windsor wouldn't have been hit with a big estate tax bill. But they were two women, and the Defense of Marriage Act (DOMA) prohibited the federal government from recognizing their relationship. Ms. Windsor owed the Internal Revenue Service $363,053.

No government interest could justify such punitive discrimination, and, increasingly, federal courts are saying so. A week ago the 2nd Circuit Court of Appeals in New York, which considered Ms. Windsor's case, ruled that DOMA violates the Constitution's guarantee of equal protection. That followed a similar result from the 1st Circuit.

After centuries of cold discrimination, American attitudes are shifting, and faster than seemed possible only a decade ago. Ms. Windsor's success is only the latest sign. Recent polls indicate that a majority of Americans, albeit a slim one, now favors same-sex marriage. Four states will hold referendums next month on permitting same-sex marriage; polls suggest that proponents have a shot. For the first time, a sitting president has said he favors same-sex marriage, the same president who eliminated the military's "don't ask, don't tell" policy.

Still, what role judges should play in this great thaw is a tricky question. Despite the movement in polls, nearly half the country still opposes same-sex marriage. In 32 states gay-rights advocates have lost at the ballot box, most recently in North Carolina in May. There is natural resistance to changing traditional institutions that provide structure and meaning to so many lives.

Federal courts have so far handed down rulings that make incremental rather than sweeping progress toward enshrining equality for gay Americans as a constitutional guarantee. Though they both repudiated DOMA, the 1st and 2nd Circuits also insisted that their words could not be interpreted to invalidate the will of states that refuse to acknowledge gay commitments.

Same-sex equality will ultimately be more durable if it is not seen as an imposition on an unwilling public by an unelected judiciary.

If the Supreme Court considers Ms. Windsor's case on appeal, and the justices are swayed in her favor, they, too, will have to decide: incremental or sweeping.