In a groundbreaking 5-4 decision, the Supreme Court ruled today that the Constitution recognizes same-sex couples' right to marry.

You can read the entire opinion, authored by Justice Kennedy, here—but the Washington Post pulled out some highlights that we're sharing.

Kennedy starts out with a passage about the Constitution's promise to Americans.

The Constitution promises liberty to all within its reach, a liberty that includes certain specific rights that allow persons, within a lawful realm, to define and express their identity. The petitioners in these cases seek to find that liberty by marrying someone of the same sex and having their marriages deemed lawful on the same terms and conditions as marriages between persons of the opposite sex.

He also made an excellent point about how society evolves.

The nature of injustice is that we may not always see it in our own times. The generations that wrote and ratified the Bill of Rights and the Fourteenth Amendment did not presume to know the extent of freedom in all of its dimensions, and so they entrusted to future generations a charter protecting the right of all persons to enjoy liberty as we learn its meaning.

When new insight reveals discord between the Constitution’s central protections and a received legal stricture, a claim to liberty must be addressed.

Kennedy cited “four principles and traditions” in the Court's decision.

1. A first premise of the Court’s relevant precedents is that the right to personal choice regarding marriage is inherent in the concept of individual autonomy. . . . Like choices concerning contraception, family relationships, procreation, and childrearing, all of which are protected by the Constitution, decisions concerning marriage are among the most intimate that an individual can make.

2. A second principle in this Court’s jurisprudence is that the right to marry is fundamental because it supports a two-person union unlike any other in its importance to the committed individuals.

3. A third basis for protecting the right to marry is that it safeguards children and families and thus draws meaning from related rights of childrearing, procreation, and education. . . .

4. Fourth and finally, this Court’s cases and the Nation’s traditions make clear that marriage is a keystone of our social order. Alexis de Tocqueville recognized this truth on his travels through the United States almost two centuries ago:

This seems to be the heart of the opinion.

Same-sex couples are consigned to an instability many opposite-sex couples would deem intolerable in their own lives. As the State itself makes marriage all the more precious by the significance it attaches to it, exclusion from that status has the effect of teaching that gays and lesbians are unequal in important respects.

It demeans gays and lesbians for the State to lock them out of a central institution of the Nation’s society. Same-sex couples, too, may aspire to the transcendent purposes of marriage and seek fulfillment in its highest meaning.

The limitation of marriage to opposite-sex couples may long have seemed natural and just, but its inconsistency with the central meaning of the fundamental right to marry is now manifest. With that knowledge must come the recognition that laws excluding same-sex couples from the marriage right impose stigma and injury of the kind prohibited by our basic charter.

These considerations lead to the conclusion that the right to marry is a fundamental right inherent in the liberty of the person, and under the Due Process and Equal Protection Clauses of the Fourteenth Amendment couples of the same-sex may not be deprived of that right and that liberty. The Court now holds that same-sex couples may exercise the fundamental right to marry. No longer may this liberty be denied to them.

And here’s the conclusion:

No union is more profound than marriage, for it embodies the highest ideals of love, fidelity, devotion, sacrifice, and family. In forming a marital union, two people become something greater than once they were. As some of the petitioners in these cases demonstrate, marriage embodies a love that may endure even past death. It would misunderstand these men and women to say they disrespect the idea of marriage. Their plea is that they do respect it, respect it so deeply that they seek to find its fulfillment for themselves. Their hope is not to be condemned to live in loneliness, excluded from one of civilization’s oldest institutions. They ask for equal dignity in the eyes of the law. The Constitution grants them that right.

We should also reference Justice Roberts' dissent, distasteful as it may be.

...This Court is not a legislature. Whether same-sex marriage is a good idea should be of no concern to us.

Under the Constitution, judges have power to say what the law is, not what it should be. The people who ratified the Constitution authorized courts to exercise “neither force nor will but merely judgment.”

Although the policy arguments for extending marriage to same-sex couples may be compelling, the legal arguments for requiring such an extension are not. The fundamental right to marry does not include a right to make a State change its definition of marriage. And a State’s decision to maintain the meaning of marriage that has persisted in every culture throughout human history can hardly be called irrational.

In short, our Constitution does not enact any one theory of marriage. The people of a State are free to expand marriage to include same-sex couples, or to retain the historic definition.

Roberts added that "those who believe in a government of laws, not of men, the majority’s approach is deeply disheartening."

Read the full Supreme Court opinion is here.