When the Supreme Court handed down its decision in King v. Burwell, the health care case, last Thursday, there was no end of talk about how the court had just cemented a critical part of President Barack Obama’s legacy. But the health care decision wasn’t the only one that will rightly be considered an important part of Obama’s legacy. The other is marriage equality—and not only because of what the president did, but also because of what he didn’t do.

Obama made headlines in 2012 when he revealed that his opinion on marriage equality had “evol[ved]” and that he now supported it. (Vice President Joe Biden may have helped speed along the president’s public evolution when he announced a few days earlier that he was “absolutely comfortable” with the idea of marriage equality and that gay and lesbian couples “are entitled to the same exact rights” as heterosexual couples.) This was a huge moment, and the president and vice president both deserved the considerable credit they received for making their support for marriage equality public. Even though their views surely reflected what was then an ongoing shift in public opinion, their announcement likely helped continue the move toward greater support for marriage equality. Indeed, by the time the Supreme Court heard oral argument in the marriage equality case in April, support for marriage equality was at a record high.

But that’s not the only reason Obama deserves some of the credit for last week’s decision in Obergefell v. Hodges (along with the justices who reached it, the marriage equality advocates who’ve been fighting for this day for decades, and the Framers of the 14th Amendment who embedded a commitment to equality and liberty in our Constitution). Another reason Obama deserves some of the credit is because of a decision he made the year before he announced his support for marriage equality: the decision not to defend in court a key provision of the federal Defense of Marriage Act, which defined marriage as the union of a man and a woman for purposes of federal law. Because of that provision, same-sex couples who were legally married under their state’s law still couldn’t enjoy the numerous and important federal benefits enjoyed by other married couples. 

In February 2011, after two years of defending that provision of DOMA in court, the Justice Department announced that it would no longer do so. At the time, Attorney General Eric Holder announced that the president had concluded that the provision of DOMA was unconstitutional as applied to legally married same-sex couples. The president thus instructed the Department of Justice not to defend the law, even though the federal government “has a longstanding practice of defending the constitutionality of duly-enacted statutes if reasonable arguments can be made in their defense.”

The president came under attack for that decision, and not just from Republicans or opponents of marriage equality. One liberal law professor wrote, for example, that “[w]hile DOMA is a discriminatory law and should be repealed, Obama’s decision not to defend it should be condemned.” He warned that “[t]his sets a terrible precedent that could well come back to haunt those who are cheering the president’s decision.” But as I wrote at the time in the Northwestern University Law Review, the president’s decision not to defend a law he believed unconstitutional was entirely proper and, in fact, a decision to be celebrated, not condemned. The executive branch, I wrote, “should be able to articulate its own best view of the law not only to influence the courts, but also to make its view of the law clear to the general public.” By doing exactly that in cases involving DOMA, the president helped bring us where we are today.

In 2013, one of the legal challenges to this key provision of DOMA reached the Supreme Court in United States v. Windsor. In that case, the government not only declined to defend the law, it actually filed a forceful brief arguing that it was unconstitutional and should be struck down. The court agreed and, in a 5-4 decision, held the provision of DOMA at issue violated the Constitution’s broad equality guarantee. As the court explained, the federal law impermissibly demeaned those same-sex couples who “wanted to affirm their commitment to one another before their children, their family, their friends, and their community.” One can’t say for sure what role the federal government’s position played in the court’s decision, but that it was willing to take the relatively rare step of declining to defend a federal law—and instead explain why it was unconstitutional—surely didn’t hurt. 

And it’s difficult to imagine the country being where it is today without the court’s decision two years ago in Windsor. Indeed, when the court decided Windsor, Justice Scalia predicted in his dissent where the decision would lead: “the view that this Court will take of state prohibition of same-sex marriage is indicated beyond mistaking by today’s opinion,” he wrote. He even identified selected passages from the majority’s opinion that he said could be just as easily applied to state laws prohibiting same-sex marriage as to the federal law at issue in Windsor. To Scalia, what would follow from the court’s decision was obvious: “As far as this Court is concerned, no one should be fooled; it is just a matter of listening and waiting for the other shoe.” And he was right: In the two years since Windsor was decided, almost every lower court to consider a challenge to a state law denying same-sex couples the freedom to marry concluded that the law was unconstitutional, often relying on the court’s reasoning in Windsor.

When the court issued its marriage equality decision in Obergefell, it was clear that the resounding chorus of lower court opinions recognizing that the Constitution mandates marriage equality had played a prominent role in the decision. The court noted that “[n]umerous cases about same-sex marriage have reached the [lower courts] in recent years,” and “[t]hat case law helps to explain and formulate the underlying principles” the court considered in Obergefell. Indeed, the majority went so far as to include an appendix listing all those decisions, many of which followed the court’s decision in Windsor. Thus, just as Windsor helped lay the path for numerous lower court decisions recognizing marriage equality, those lower court decisions in turn helped lay the path for the Supreme Court’s decision last week in Obergefell, including its powerful conclusion that gay and lesbian couples seeking the right to marry “ask for equal dignity in the eyes of the law. The Constitution grants them that right.”

So while there are many people who deserve credit for the court’s historic decision in Obergefell, there’s one more who should go on the list: President Barack Obama. He deserves credit not just for the powerful support his administration provided in Obergefell itself, but also for his decision not to defend DOMA four years earlier. It’s a helpful reminder of the power of the presidency, and how it can play out in unexpected ways.