His prose may lack the fiery eloquence of his US supreme court colleagues Ruth Bader Ginsburg and Antonin Scalia, or the razor-sharp precision of chief justice John Roberts, but the majority opinion written by Justice Anthony Kennedy – granting a constitutional right to same-sex marriage across the United States – will go down as one of the most important legal documents in the history of the American civil rights struggle.



Court-watchers were left in little doubt where most of the nine justices stood on marriage equality after two and a half hours of extended oral arguments held the hushed halls of the nation’s highest tribunal spellbound in April.



On one side, the court’s traditional liberals: Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan were withering in their view of the arguments advanced by Republican-controlled states that wanted to hold back the growing tide of legal rulings that backed gay marriage.

On the other side of the bench were the more reliably conservative members of the supreme court – Scalia, Samuel Alito and the typically silent Clarence Thomas – who believed not just that marriage should remain solely between a man and woman, but that the court had no right to voice its opinion on the matter at all.

More inscrutable, however, were Roberts, who barely said a word throughout the entire hearing, and Kennedy, who seemed genuinely unsure which way to lean: he expressed concern for the consequence of either ruling.

Kennedy, the 78-year-old former lawyer from California appointed to the bench by Republican president Ronald Reagan a generation ago, is seen – in theory – as one of the conservative majority. But in practice, he has long been the most enigmatic of the swing voters on some of the most defining stories in American history.

On Thursday, he had joined Roberts in defending Barack Obama’s healthcare reforms from yet another legal onslaught by conservative critics.

But on Friday, the day same-sex marriage became the law of the land, Roberts had decided to stay firmly in the conservative camp.

And so Kennedy became the one man to effectively determine a decision that will directly affect millions of Americans in love – and redefine a core legal and social bedrock for all of them, perhaps forever.

For a while, it looked as if the swing voters might have coalesced around a compromise on marriage equality, forcing all states to recognise same-sex marriages carried out elsewhere but still shying away from forcing them to carry it out themselves against the wishes of their voters.

This democratic challenge was of particular concern to Roberts, who was the swing vote in earlier judgments that upheld gay rights, but is known to be wary of polarizing the court’s reputation by appearing to override state autonomy.

Campaigners were hopeful that Kennedy might prove bolder, particularly after his earlier support for gay rights in cases that longtime observers of the court believed would build up to the moment they had been waiting to arrive for so long.

He did.

From discrimination in Colorado to sodomy in Texas to the words that changed a country

Chief justice John Roberts (left) and Anthony Kennedy (middle), the swing consciences of the US supreme court. Photograph: Charles Dharapak/Pool/Cnp/Charles Dharapak/Pool/Cnp/ZUMA Press/Corbis

Kennedy’s first flick in the direction of LGBT rights came in the 1996 case of Romer v Evans, when he authored a ruling striking down a constitutional amendment in the state of Colorado that barred efforts by local governments to discriminate against gay and lesbian people. The amendment, Kennedy wrote at the time, “classifies homosexuals not to further a proper legislative end but to make them unequal to everyone else”.

He went on to author the opinion in a 2003 ruling that invalidated an anti-sodomy law in Texas, in which Kennedy argued that intimate relationships between gay couples “involves liberty of the person both in its spatial and more transcendent dimensions”.

“It suffices for us to acknowledge that adults may choose to enter upon this relationship in the confines of their homes and their own private lives and still retain their dignity as free persons,” Kennedy wrote. “When sexuality finds overt expression in intimate conduct with another person, the conduct can be but one element in a personal bond that is more enduring.”

Two years ago, Kennedy’s evolution in support of gay rights seemed all but final with the landmark United States v Windsor case that struck down key components of the Defense of Marriage Act (Doma) and was viewed as the forerunner to legal same-sex marriage nationwide.

The federal government’s refusal to afford same-sex couples the same benefits offered to heterosexual couples “tells those couples, and all the world, that their otherwise valid marriages are unworthy,” Kennedy wrote. “And it humiliates tens of thousands of children now being raised by same-sex couples.”

But where Kennedy might ultimately settle down this time – for the big one – remained a mystery until shortly after 10am on Friday, when the court surprised everyone by pulling its biggest decision of the decade out of the hat three days earlier than expected.

A powerful re-affirmation of dignity

Any hope that Roberts might have had of preserving court unity was lost when four boxes of judgments materialised on Friday morning – one for the majority opinion written by Kennedy and the four liberals, and the others for an unprecedented four separate dissents from the conservative wing of the bench.

They may have differed in their precise reasons for opposing the decision, but these dissents, including a blunt warning from Roberts, were unusually withering.

Key parts of the majority opinion contained little more than “the mystical aphorism of the fortune cookie”, fumed Scalia.

But Kennedy was undeterred, drawing on repeated examples of the court’s previous evolution on the subjects of marriage and civil rights to argue that it was time for the court to come down from off the fence on perhaps the last big outstanding civil rights question of the modern age.

Despite the dynamite conclusion of the long marriage equality fight at the supreme court, it was a dry legal argument that conveyed the news.

The closest Kennedy came to capturing the emotion felt by campaigners and protesters on both sides of the argument was when he was describing the institution at the heart of the argument.

“No union is more profound than marriage, for it embodies the highest ideals of love, fidelity, devotion, sacrifice and family,” he wrote. “In forming a marital union, two people become something greater than once they were.”

Those who know the court best are in little doubt as to the significance of Kennedy’s words.

“It may be the most consequential decision by the Court in a generation or more,” said former US solicitor general Neal Katyal. “The Court powerfully reaffirmed the equal dignity of all to marry today; and this is a decision that will be read hundreds of years from now.”

Roberta Kaplan, the attorney who successfully argued the Doma case, told the Guardian: “I can’t imagine this being a better decision.”

It also capped an avalanche of legal and cultural change on an issue that has in recent years caught even the fiercest proponents of same-sex equality by surprise.

“Today’s decision acknowledging the right of same-sex couples to marry is the culmination of decades of litigation and the fastest shift in public opinion in American history,” said Nicole Pearl, a Los Angeles lawyer who specialists in estate and tax planning for gay, lesbian and unmarried couples.

But on a day when a funeral for victims of the Charleston church shootings cast a long shadow over the ongoing battle for racial equality, the decision was a source of hope for many.

“America should be very proud,” said Barack Obama in an emotional statement from the White House rose garden.

“There’s so much more work to be done to extend the full promise of America to every American,” he added. “But today, we can say in no uncertain terms that we’ve made our union a little more perfect.”