The first case I litigated before Justice Anthony Kennedy, who announced his retirement on June 27 after more than 30 years on the Supreme Court, was Texas v. Johnson, the 1989 case that established that the First Amendment protects flag-burning. Kennedy, a mild-mannered Reagan appointee, was no flag-burner. But he provided the crucial fifth vote to strike down Texas’s law.1

A few years later, I invited him to guest-teach my constitutional-law class at Georgetown. I said he could talk about anything; he chose the flag-burning case. But his real subject was judging. In his hour with the students, he not only stressed the importance of having an open mind, but exemplified it in his openness to the students themselves. Not all judges are like this; Justice Antonin Scalia was always absolutely certain about his views when speaking to students (or to anyone else, for that matter).2

I remember arguing to a colleague, a noted gay-rights scholar, that this characteristic meant that Kennedy might be persuaded to vote in favor of other progressive causes. My colleague dismissed the idea, sure that Kennedy would play to type and vote consistently conservative.3

Yet it was Kennedy who wrote every one of the Court’s decisions protecting gay and lesbian rights, including pathbreaking decisions striking down a Colorado referendum that barred protection against discrimination on the basis of sexual orientation, and invalidating a Texas law making same-sex “sodomy” a crime. And most importantly, he wrote the majority opinions in United States v. Windsor and Obergefell v. Hodges, both 5–4 decisions extending constitutional protection to the marriage of same-sex couples. In these and other decisions, he saw in anti-LGBTQ measures a direct affront to the equal dignity of all persons.4

Justice Kennedy’s role in these cases is often overstated. The Court’s recognition of gay rights, and especially marriage equality, was largely attributable to changes outside the Court—in the world at large and the American public in particular. And the champions of those changes were the individuals and organizations that fought for equal respect for gay and lesbian people and relationships for decades, in city-council meetings, corporate boardrooms, state courts and legislatures, ballot-initiative campaigns, and, of course, the streets. But Kennedy, an unlikely ally, was open to acknowledging that the world had changed.5

To do so, Kennedy also had to be receptive to the concept of an evolving Constitution, not limited to the specific (and historically constrained) ideas of those who adopted it more than 200 years ago. As he wrote in Obergefell:6

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.7

Still, Kennedy was a conservative. One study identified him as the 10th most conservative justice since 1937. On business cases, he almost always sided with corporations. He also cast crucial votes to gut the Voting Rights Act in Shelby County v. Holder, to strike down portions of the Affordable Care Act, to nullify campaign-finance restrictions on corporations in Citizens United v. FEC, and often to uphold states’ immunity from individuals seeking remedies for violations of their rights. This term, he voted with the conservatives in all 14 of the Court’s 5–4 decisions, including decisions upholding the Muslim ban and state voter purges and gravely undermining public-sector unions and workers’ rights to pursue their grievances collectively in arbitration. And probably most consequentially, he voted down the line with the Republicans in Bush v. Gore to stop the recount and ensure George W. Bush’s election in 2000—which in turn brought us the appointments of John Roberts and Samuel Alito.8

But Kennedy’s dual commitment to an open mind and an evolving Constitution meant that he not infrequently ruled in favor of liberty for the marginalized. He wrote historic opinions banning the death penalty and sentences of life without parole for juvenile offenders, and, in Boumediene v. Bush, extending habeas corpus to Guantánamo detainees—and the rule of law to the War on Terror.9

Because he was open to persuasion, Kennedy could also change his mind—much to Justice Scalia’s dismay. Despite having voted with the conservatives on a number of abortion-rights and affirmative-action cases, when directly confronted with the question of whether Roe v. Wade should be overruled or affirmative action ended, he voted with his liberal colleagues to reaffirm their proper place. In 1992, in Planned Parenthood v. Casey, he joined Justices Sandra Day O’Connor and David Souter in preserving Roe v. Wade, and thus abortion rights. And in 2016, in Fisher v. University of Texas, he voted with his liberal colleagues to preserve affirmative action, over dissents that would have declared it unconstitutional.10

Kennedy was, above all, a moderating force. Largely because of his votes, the Court remained within the mainstream of American opinion. Chief Justice Roberts and Justices Alito, Clarence Thomas, and Neil Gorsuch are deeply and reliably conservative; they only rarely join their liberal counterparts in closely divided cases. If President Trump names another rigidly right-wing justice, the Court risks becoming an outlier, far more conservative than the country at large. And that would put in peril many rights that hang by a one-vote margin, including abortion rights, affirmative action, LGBTQ equality, and freedom from the establishment of religion. We should demand that any successor show the same open mind, the same moderating temperament, and the same sensitivity to equal dignity for all that Justice Kennedy displayed.11