The first line of the U.S. Supreme Court’s decision in Obergefell v. Hodges, on the legality of same-sex marriage in the United States, is as breathtaking as it is legalistic.

The Fourteenth Amendment requires a State to license a marriage between two people of the same sex and to recognize a marriage between two people of the same sex when their marriage was lawfully licensed and performed out-of-State.

There it is, the ruling that gay-marriage advocates and opponents have been waiting for since April when the Court took up the case—but really, for years long before that. There is now a constitutional right for people of the same sex to get married in the United States.

The Court’s opinion—authored by Justice Anthony Kennedy, a Catholic who has long been seen as the possible swing vote on gay marriage, joined by Justices Stephen Breyer, Ruth Bader Ginsburg, Elena Kagan, and Sonia Sotomayor, and with four separate dissents authored and joined by combinations of  Samuel Alito, John Roberts, Antonin Scalia, and Clarence Thomas—lists four major reasons for its decision. First, Kennedy writes that “decisions about marriage are among the most intimate that an individual can make.” Allowing LGBT people to marry is a matter of personal choice and autonomy, just as it was in the Court’s 1967 decision in Loving v. Virginia, which outlawed bans on interracial marriage.

Second, Kennedy writes, marriage is a distinctive institution: “It supports a two-person union unlike any other in its importance to the committed individuals.” Here, he points to the Court’s opinion in Griswold v. Connecticut, which affirmed the right of married couples to use birth control. “Same-sex couples have the same right as opposite-sex couples to enjoy intimate association.”

But then, the decision takes an interesting turn: The Court seems to flip the oft-used reasoning of same-sex marriage opponents, who claim that gay marriage is harmful to children and families, and disruptive to the longstanding order of American society. In the oral arguments for Obergefell, several justices raised this very question—even Breyer, who joined in the decision, said that marriage between a man and a woman “has been the law everywhere for thousands of years. Suddenly you want nine people outside the ballot box to require states to change [this configuration].” But on Friday, Breyer joined four of his colleagues to do exactly that.

“Protecting the right to marry ... safeguards children and families and thus draws meaning from related rights of childrearing, procreation, and education,” Kennedy writes. Not all straight married couples have children, and they’re certainly not required to do so by law, he reasons; the same rule should apply to gay married couples. But more importantly, for those gay couples that do want to have kids—including the many couples who adopt or have children using the genetic material of one parent—that their unions are less than marriage under the law creates a “more difficult and uncertain family life. The marriage laws at issue thus harm and humiliate the children.”

“Rising from the most basic human needs, marriage is essential to our most profound hopes and aspirations.”

Finally, Kennedy affirms that marriage is “a keystone of the Nation’s social order.” It is the institution at the center of the United States’ legal and educational structures, and because of this, “it is demeaning to lock same-sex couples out of a central institution of the Nation’s society, for they too may aspire to the transcendent purposes of marriage.”

“Rising from the most basic human needs, marriage is essential to our most profound hopes and aspirations,” Kennedy writes. This is, perhaps, the most striking argument of all, for it is an argument about the nature, significance, and dignity of marriage itself. “The ancient origins of marriage confirm its centrality, but it has not stood in isolation from developments in law and society,” Kennedy writes, but the “institution—even as confined to opposite-sex relations—has evolved over time.”

The dissents from Alito, Roberts, Thomas, and Scalia are scathing. The chief justice argues that the Court has stepped far beyond its bounds, stating simply, “this Court is not a legislature.” Like his colleagues in the majority, he delves into the history of marriage, even giving a nod to one of the favorite arguments of gay-marriage opponents: that legalizing gay marriage is essentially a slippery slope. In fact, he writes, the leap from heterosexual marriage to same-sex marriage is “much greater than one from a two-person union to plural unions, which have deep roots in some cultures around the world.” His conclusion: “The majority expressly disclaims judicial ‘caution’ and omits even a pretense of humility, openly relying on its desire to remake society according to its own ‘new insight’ into the ‘nature of injustice.’ … Just who do we think we are?”

Scalia’s dissent carries a much more mocking tone—indeed, he says he concurs with Roberts entirely, but is writing a separate dissent to “call attention to this Court’s threat to American democracy.” He diagrams several of Kennedy’s sentences and states his astonishment at “the hubris reflected in today’s judicial Putsch.” His main objection is that the Court has stepped beyond the boundaries of the law—not just in Obergefell, but over the course of several recent decisions. “With each decision of ours that takes from the People a question properly left to them—with each decision that is unabashedly based not on law, but on the ‘reasoned judgment’ of a bare majority of this Court—we move one step closer to being reminded of our impotence,” he writes.

“The majority and omits even a pretense of humility ... Just who do we think we are?”

And there were hints of the battles ahead. In each of their dissents, Thomas and Alito address the question of religious liberty, arguing that this decision will make it much more difficult for those who oppose gay marriage on the basis of faith to exercise their beliefs. “It will be used to vilify Americans who are unwilling to assent to the new orthodoxy,” Alito writes. “In the course of its opinion, the majority compares traditional marriage laws to laws that denied equal treatment for African-Americans and women. The implications of this analogy will be exploited by those who are determined to stamp out every vestige of dissent.” Thomas predicts that the decision will present challenges for churches and other religious organizations that must now determine whether to recognize civil same-sex marriages, and Roberts warns of challenging questions about the tax status of religious non-profits, like colleges, that discriminate on the basis of sexual orientation.

Let those challenges come. Opponents of same-sex marriage have long argued that the institution of marriage is sacred, and that gay unions would change its very nature. They have contended that it has been historically defined as a union between one man and one woman, and that the Court does not have the authority to change that definition. With this decision, the Supreme Court of the United States dissents.