One of the liveliest exchanges during this morning’s oral argument in the challenge to the constitutionality of California’s Proposition 8, which changed the state’s Constitution to define marriage as only between a man and a woman, came when Justice Antonin Scalia aggressively questioned the challengers’ lawyer, Ted Olson, about when such discriminatory laws “became unconstitutional.”

JUSTICE SCALIA: I’m curious, when — when did — when did it become unconstitutional to exclude homosexual couples from marriage? 1791? 1868, when the Fourteenth Amendment was adopted? Sometimes — some time after Baker [v. Nelson], where we said it didn’t even raise a substantial Federal question? When — when — when did the law become this?

MR. OLSON: When — may I answer this in the form of a rhetorical question? When did it become unconstitutional to prohibit interracial marriages? When did it become unconstitutional to assign children to separate schools.

JUSTICE SCALIA: It’s an easy question, I think, for that one. At — at the time that the Equal Protection Clause was adopted. That’s absolutely true. But don’t give me a question to my question. When do you think it became unconstitutional? Has it always been unconstitutional? . . .

MR. OLSON: It was constitutional [sic] when we -¬ as a culture determined that sexual orientation is a characteristic of individuals that they cannot control, and that that -¬

JUSTICE SCALIA: I see. When did that happen? When did that happen?

MR. OLSON: There’s no specific date in time. This is an evolutionary cycle.

Ted Olson is a brilliant and fantastic lawyer. And he gave a powerful performance this morning. But his response to Justice Scalia missed a major opportunity to show how the original meaning of the Constitution supports marriage equality.

The simple answer to Justice Scalia is that laws banning same-sex couples from marrying were unconstitutional the moment when the American people, in 1868, wrote the guarantee of equality for all persons into the Constitution. As the exchange this morning demonstrates, Justice Scalia seems to accept this proposition with respect to laws prohibiting couples from different races from marrying one another, which the Supreme Court found unconstitutional in the late 1960s. He should acknowledge the same constitutional truth in the Prop. 8 case. The text of the Equal Protection Clause of the Fourteenth Amendment makes clear that the freedom to marry should be equally available to all, whether black or white, heterosexual or gay, rich or poor.

The Equal Protection Clause provides: “No State shall . . . deny to any person within its jurisdiction the equal protection of the laws.” Drafted in 1866 and ratified in 1868, the Clause wrote into the Constitution the ideal of equality first laid out in the Declaration of Independence. It established a broad guarantee of equality for all persons and demanded, as Olson reminded the Justices this morning by invoking Justice Ginsburg’s eloquent opinion in the Virginia Military Institute case, “the extension of constitutional rights and protections to people once ignored or excluded.” While race was obviously at the forefront of the minds of the Amendment’s drafters–after all, they had just secured an amendment banning slavery in the wake of a brutal civil war–they specifically chose language that would protect against unequal treatment based on more than just racial discrimination, and in fact affirmatively rejected narrower proposals that would prohibit only racial discrimination.

Even so, had Olson given Justice Scalia the answer I have suggested, Scalia surely would have retorted that there was no way the American people were thinking of marriage equality for gay and lesbian couples when they ratified the Amendment. That’s not the point. No originalist–not even Justice Scalia–believes that the plain words of the Constitution apply only in the ways the framers expected. The ruling Justice Scalia announced from the bench just before the start of arguments this morning is a perfect example: just because there weren’t drug-sniffing police dogs in 1791, doesn’t mean their use can’t violate the Fourth Amendment’s protection against unreasonable searches and seizures, as the Court held today in Florida v. Jardines.

The Constitution guarantees equal protection of the laws to “any person.” In looking to what rights were understood to be protected equally, the framers of the Fourteenth Amendment understood state-sanctioned marriage as a personal, individual right that must be made available on an equal basis to all persons. Accordingly, by writing into the Constitution a requirement of equality under the law and equality of basic rights for all persons, which included the right to marry, the Amendment’s framers ensured that discriminatory state laws would not stand in the way of Americans exercising their right to marry the person of their own choosing. Laws that discriminate and deny to members of certain groups, including gays and lesbians, the right to marry the person of one’s choice thus contravene the original meaning of the Fourteenth Amendment.

It may have taken us 100 years to get it right with respect to race-restrictions on the freedom to marry, but it doesn’t mean those laws weren’t unconstitutional in 1868. The same is true, nearly 150 years after the ratification of the Fourteenth Amendment, for laws that deny gay and lesbian couples the freedom to marry. I only wish Justice Scalia had been forced to face this constitutional text and history head on this morning.