Ronald Rotunda is a professor at Chapman University's Fowler School of Law.

The Supreme Court allowed President Trump's travel ban to go into effect this week, overturning a lower court ruling as a federal appeals court considers the issue. Justice Ruth Bader Ginsburg dissented and did not disqualify herself from that preliminary decision. Two questions emerge: First, why not? And second, will she disqualify herself if the court takes the case?

We already know what Ginsburg thinks of the president. She told us more than a year ago that she "can't imagine what the country would be . . . with Donald Trump as our president." Facing criticism for her apparent endorsement of Hillary Clinton and her attacks on Trump, Ginsburg doubled down, emphasizing in a CNN interview: "He is a faker." She then went on "point by point, as if presenting a legal brief," the CNN analyst said.

Her statements are particularly troubling in the context of the travel ban case, in which the crucial issue — at least, according to the lower courts and the plaintiffs — is the personal credibility of Trump and whether he delivered his executive order in good faith — in other words, whether he is faking it. It's no wonder 58 House Republicans sent Ginsburg a letter calling for her recusal because of her comments before the election.

Given these facts, Ginsburg should heed her critics — either by recusing herself from the case or explaining to the public why she will not.

When disqualification was first raised, a bevy of academics argued that she should not disqualify herself simply because she, in effect, endorsed Trump's opponent and presumably did not vote for Trump. However, the issue is not whether she should disqualify herself in all cases where the president is a party. It is whether she should disqualify herself in a case where the issue is whether the president's "motives" are sincere, when she has already concluded that he is not.

Lower courts have conceded that Trump's reasons are "facially legitimate," but concluded that they were made in "bad faith" and not "bona fide." They rely on a series of statements by Trump on the campaign trail. For example, the court points to an interview in March 2016 in which Trump said he thinks "Islam hates us."

Although no version of the president's executive order bans all Muslims, the court says that Trump really intends to do that. When he recharacterized his call to ban Muslims as a ban on nationals from certain countries or territories, the court said it did not believe him. Instead, the court will discern his true motive, because "six countries [out of eight in the ban] have overwhelmingly Muslim population." In other words, the lower court agrees with Ginsburg that Trump is a "faker."

The Justice Department has not called for her disqualification, but it's not unusual for an institutional litigant (one that regularly appears before this court) to be reluctant to antagonize a justice by demanding disqualification.

Still, the Code of Conduct for U.S. judges states that a judge shall not "make speeches for a political organization or candidate, or publicly endorse or oppose a candidate for public office," and it sure looks like Ginsburg violated that provision. The code also insists that judges avoid "impropriety and the appearance of impropriety in all activities." Technically, the code does not apply to the Supreme Court, but Chief Justice John G. Roberts Jr. has assured us that he and his fellow justices follow it.

In 2004, after efforts to force Justice Antonin Scalia to recuse himself in a case because he had gone duck hunting with then-Vice President Dick Cheney, Scalia carefully wrote an opinion explaining why he was not disqualifying himself where Cheney's own conduct is not "central to this case." Indeed, he wrote: "Nothing this court says on those subjects will have any bearing upon the reputation and integrity of Richard Cheney."

But that is not true of the travel ban case. If Ginsburg believes that she should not recuse herself, it would be helpful to the nation if she explains why. Just as Scalia's opinion against his disqualification, Ginsburg can explain her decision, so the public can evaluate her reasons for itself.