In the chorus of voices raising concerns about President Donald Trump’s attacks on the judges who halted his administration’s travel ban, an important one has been notably absent: Chief Justice John Roberts.

As the leader of the federal courts, the Chief Justice plays a significant role in defending them. In fact, at Roberts’ own confirmation hearing in 2005, he promised that “to the extent the judiciary is attacked, I will be vigilant to respond and defend it.”

With America’s judiciary in the spotlight this week, and in the wake of Trump’s recent comments, the need for such a response and defense is more urgent now than ever.

Unlike elected officials, judges have limited ability to defend themselves. Their commitment to impartiality requires them to remain above the fray. Judicial decisions are explained in carefully crafted opinions, not tweets or press conferences. As a result, judges rely on others to remind the public, and occasionally politicians, of the importance of judicial independence in a democracy.

One of those people is actually the nation’s top judge, who is not only a judge but the leader of the federal judiciary. In that role, Chief Justice Roberts has a unique platform to be a voice in its defense. Indeed, at his confirmation hearing Roberts explained that the Chief Justice has an “important educating function” to explain “that what judges do promotes the rule of law and that the rule of law preserves liberties for all Americans.”

At his confirmation hearing Roberts said the Chief Justice has an “important educating function” to explain “that what judges do promotes the rule of law and that the rule of law preserves liberties for all Americans.” While emphasizing that “it’s perfectly appropriate” and even “healthy” for “people to criticize decisions of judges,” Roberts explained that “judges — and certainly even judges with whom I disagree on the results or particular merits, they should not be attacked for their decisions.” And he said he would “be vigilant to protect the independence and integrity of the Supreme Court and the judicial branch.”

In embracing the notion of the Chief Justice as an explainer and defender of the courts, Roberts followed in the footsteps of his predecessor and mentor, the late Chief Justice William Rehnquist. Rehnquist, who described judicial independence as “one of the crown jewels of our system of government,” spoke out in those moments during his tenure when the judiciary was under attack.

For example, in the 1996 presidential election, both presidential candidates suggested that a federal district court judge should be forced from the bench for an unpopular ruling. In a speech at American University, Rehnquist offered a gentle but clear rebuke, recounting the story of the 1805 Senate trial of Supreme Court Justice Samuel Chase. Breaking from President Thomas Jefferson, the Senate refused to remove Chase based on his rulings. Rehnquist described the decision as “enormously important in securing . . . judicial independence” and providing “assurance to federal judges that their judicial acts . . . would not be a basis for removal from office.”

Similarly, Rehnquist used his 2004 year-end report on the federal judiciary to express his concern about congressional threats to impeach some judges and limit the judiciary’s ability to hear certain cases. Noting that criticism of judges “is as old our republic,” he added that for over 200 years, judicial independence “has served our democracy well and ensured a commitment to the rule of law.”

Today, judicial independence is once again under attack. Over the past two months, President Trump has repeatedly made statements that delegitimize judges and courts. In addition to attacking the “so-called” judge who stayed his administration’s travel ban, he has also suggested that the courts are “so political,” and should be blamed for any terror attacks.

Chief Justice Roberts should use his platform to respond to these recent attacks — not by commenting on the merits of any particular incident, but by drawing attention to the fact that such hyperbolic criticism threatens our system of co-equal branches of government.

Comments suggesting that judges are biased, or that the judiciary acts improperly when it rules the government has violated the law, put democracy at risk. At a moment when the judiciary is under assault, the Chief Justice should embrace his role as a “vigilant” defender of the courts — and respond.

Kalb is a Fellow in the Democracy Program at the Brennan Center for Justice at NYU School of Law and Associate Professor of Law at Loyola University New Orleans College of Law. Bannon is Senior Counsel in the Democracy Program at the Brennan Center for Justice at NYU School of Law.

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