This one is for the ages.

Justice Anthony Kennedy's opinion for the U.S. Supreme Court announcing a right to gay marriage in Obergefell v. Hodges will take its place alongside Brown v. Board of Education and Loving v. Virginia in the pantheon of great liberal opinions.

The only tragic contrast with those landmarks in the history of equality is that both of those were decided unanimously. Friday's gay- rights opinion went 5-4, with each of the court's conservative justices writing a dissent of his own. Eventually, legal equality for gay people will seem just as automatic and natural as legal equality for blacks. But history will recall that when decided, Obergefell didn't reflect national consensus, much less the consensus of the court itself.

ColumnFiller: At the court, a victory for liberty and freedomCartoonsCartoonists debate same-sex marriage

Kennedy's opinion offered two different yet interrelated constitutional rationales, one focused on the institution of marriage, the other on the equality of gay people.

First, he made the case that marriage is a fundamental liberty right under the due process clause of the Constitution, which says no one may be deprived of life, liberty or property without due process of law. Applying what's known as "substantive" due process analysis, Kennedy held that the government may not infringe the liberty to marry absent a compelling interest and along narrowly tailored lines to achieve that interest. Because no such interest exists, gay people as well as straight people must have the right to marry. This same approach was used by the court in the Loving case, which struck down laws barring interracial marriage. It was symbolically important for Kennedy to connect same-sex marriage to marriage between the races.

Kennedy's favorite concept of dignity figured large in the finding that marriage is a fundamental right. "The lifelong union of a man and a woman always has promised nobility and dignity to all persons, without regard to their station in life."

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The reference to dignity connected the decision to Kennedy's earlier gay-rights decisions, which featured the concept centrally. It is now an important part of our constitutional law -- no matter that it doesn't appear in the Constitution.

Another crucial feature of the opinion was Kennedy's recognition that marriage has evolved over time. This acknowledgement counteracted the conservatives' emphasis on tradition in their dissents. It also resonated with the doctrine of due process, which looks to evolving tradition to identify the content of protected liberty.

When it came to equality, Kennedy avoided announcing that laws burdening gay people would be subject to especially strict scrutiny, like laws burdening racial minorities, or even what's called intermediate scrutiny, like laws differentially burdening the sexes. Instead, he spoke of the "synergy" between due process and equality. In legal terms, this almost certainly meant that once a fundamental right is invoked, any distinction between people for any reason requires strict scrutiny -- a longtime doctrinal norm.

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But Kennedy didn't quite say so, probably because he wanted to preserve the legacy of earlier gay-rights opinions in which he never said that he was engaged in close scrutiny, but rather said that the laws were discriminatory on their face. In a sense, Kennedy in Friday's opinion was trying to defend and sharpen the legal rationales of those earlier decisions, which have been criticized especially strongly by Justice Antonin Scalia.

Scalia, of course, led the conservative charge in his dissent.

"What really astounds," he wrote, "is the hubris reflected in today's judicial Putsch."

The topic of gay rights apparently puts Scalia in mind of the German language -- dissenting from Kennedy's first gay-rights opinion, Romer v. Evans, he accused the court of mistaking a "kulturkampf for a fit of spite." Scalia was at pains to insist that he wasn't homophobic, just indifferent to gay rights. "The substance of today's decree is not of immense personal importance to me," he insisted.

What was really at stake according to Scalia was democracy itself. Nine unrepresentative justices made the decision, or rather a subset of them. Scalia, a New Yorker who went to Harvard Law School, criticized the fact that all the members of the current court went to Harvard or Yale law schools and that four of them are from New York, while none is an evangelical or any kind of Protestant at all. The irony of Scalia, an opponent of affirmative action, presenting himself as an advocate for diversity on the Supreme Court is, well, noteworthy.

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Chief Justice John Roberts's dissent was more to the point. Roberts has a legitimate legacy as an advocate of judicial restraint, as he demonstrated Thursday in upholding the Affordable Care Act for the second time.

Logically, then, Roberts was in a position to criticize Kennedy's opinion for judicial activism -- which it unquestionably is. Roberts cited one of the Supreme Court's most derided opinions, Lochner v. New York, in which a property-protecting libertarian majority struck down a working-hours-limitation law for violating what it called the "liberty of contract."

Among lawyers, the Lochner case stands for unbridled activism and the imposition of an ideology not found in the Constitution. Analytically, Roberts is right that Friday's decision reflects changing beliefs about what counts as liberty and equality.

Where he is wrong is in thinking that the public will generally reverse itself on the topic of gay rights. When it comes to equality and liberty, the modern trend is to extend rights, not contract them. Roberts's dissent is truly unfortunate, therefore, for his legacy: It reflects a commitment to judicial restraint, but in the long run it will be seen as having weighed in on the wrong side of history.

Justice Clarence Thomas dissented separately to say that there's no such thing as substantive liberty in the due process clause, and if there were, it wouldn't include gay marriage. The precedent of Loving v. Virginia was strangely absent from his opinion. Roberts said that case didn't change the basic definition of marriage -- but unlike Thomas, he didn't reject the very logic on which the Loving decision is built.

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That left it to Justice Samuel Alito to try to defend the traditional definition of marriage -- and to defend its defenders. The decision, he claimed, "will be used to vilify Americans who are unwilling to assent to the new orthodoxy." Here's hoping he's wrong about that. The truth is that religious liberty remains a central American value.

The gay-marriage decision shouldn't touch that First Amendment tradition, either legally or symbolically. The case is a victory for liberty and equality -- and that's the sort of orthodoxy everyone should be able to embrace.

Noah Feldman is a nationally syndicated columnist.