He wasn't sure yet whether same-sex relationships were "entitled to formal recognition in the law," but ruled that private sexual conduct between two consenting adults couldn't be criminalized. "When homosexual conduct is made criminal by the law of the State, that declaration in and of itself is an invitation to subject homosexual persons to discrimination both in the public and in the private spheres," Kennedy wrote for the Court.
June 26, 2013: U.S. v. Windsor
A decade after Lawrence, Kennedy's ire turned toward federal law. In a 5-4 ruling that essentially put the Court's informal stamp of approval on same-sex marriage, the Court—led by Kennedy—struck down part of the Defense of Marriage Act, which denied federal marriage benefits to same-sex couples. Kennedy's focus on dignity ratcheted up, and he also argued that DOMA was unfair to children raised by parents of the same sex.
"DOMA undermines both the public and private significance of state-sanctioned same-sex marriages; for it tells those couples, and all the world, that their otherwise valid marriages are unworthy of federal recognition," Kennedy said. "This places same-sex couples in an unstable position of being in a second-tier marriage."
By this point, a lot of legal observers—including Justice Antonin Scalia, Kennedy's chief antagonist on matters of gay rights—saw the writing on the wall. Although the Court passed on a chance in 2013 to rule on state laws banning same-sex marriage, Scalia said Kennedy's ruling against DOMA all but guaranteed that those laws would fall sooner or later.
Two years later to the day, in fact.
June 26, 2015: Obergefell v. Hodges
If Kennedy's past decisions reflected a certain restraint, to at least technically avoid answering the most fundamental questions about same-sex marriage, he let it all fly Friday.
"It demeans gays and lesbians for the State to lock them out of a central institution of the Nation's society," he wrote. "Same-sex couples, too, may aspire to the transcendent purposes of marriage and seek fulfillment in its highest meaning."
Kennedy's ruling on nationwide same-sex marriage hits all the high points: It specifically cites both Lawrence and Windsor to lay out the framework of equal treatment and the importance of marriage as a social institution—and then takes it up a notch.
"Marriage responds to the universal fear that a lonely person might call out only to find no one there. It offers the hope of companionship and understanding and assurance that while both still live there will be someone to care for the other," Kennedy wrote in one of several passages almost tailor-made for readings at a wedding ceremony.
The trend toward broader acceptance of same-sex marriage, both legally and in public opinion, started to move a lot faster in the two years following the Court's ruling in Windsor. Indeed, Kennedy's first question during oral arguments in Obergefell was about the wisdom of changing a definition of marriage that "has been with us for millennia."
But his decision specifically rejects the charge that the Court might be moving too quickly, by casting marriage as a right too important to leave up to legislatures.
"While the Constitution contemplates that democracy is the appropriate process for change, individuals who are harmed need not await legislative action before asserting a fundamental right," Kennedy said.