In a country dedicated to the rule of law, it is disheartening to see a U.S. Supreme Court justice ignore basic conflict-of-interest principles.

No, we are not talking about Justice Antonin Scalia, who went on a now-famous Louisiana duck hunting junket with Vice President Dick Cheney even though Cheney had a sensitive case pending in the Supreme Court at that time. Scalia has refused to disqualify himself from Cheney’s case, arguing that his friendship with the vice president is irrelevant in a “run-of-the-mill” legal dispute about an administrative decision. Although we disagree with Scalia’s decision, it is still just an error of judgment limited to a single case.

The deeper problem is with Chief Justice William H. Rehnquist, who is perpetuating a rule that prevents such errors from ever being corrected. He has committed the Supreme Court to an each-justice-decides-alone position that places individual decisions beyond review.

A federal statute requires Supreme Court justices to disqualify themselves in any case in which their “impartiality might reasonably be questioned.” In January, Sens. Patrick J. Leahy, D-Vt., and Joe Lieberman, D-Conn., wrote a letter to Rehnquist asking about the court’s procedures for implementing this rule regarding the Scalia-Cheney duck hunt. Unfortunately, Rehnquist brushed off their concerns about Scalia’s impartiality as “ill considered.” He admonished the senators that “it has long been settled that each justice must decide such a question by himself.”

That is a mischaracterization. In the world of law, an issue becomes “settled” only after it has been fully litigated and decided by a court, usually with a well-reasoned written opinion that takes competing interests into account. That has not happened with the Supreme Court’s recusal policy, which has never been the subject of any litigation or even public discussion. It would be fair to call the policy “long entrenched” but it cannot be called “settled.”

Apart from the nine Supreme Court justices, no other judge in the United States exercises unreviewable discretion when his or her impartiality is questioned; if a litigant wants a federal district court judge recused, for example, that decision is always made by another judge in the district. There is no good reason why the members of the Supreme Court would arrogate such power to themselves. Human beings, after all, are notoriously bad at evaluating their own motives or objectivity, and worse still when it comes to assessing public reactions.

The justices disagree with one another all the time, often quite sharply. That is why we have a nine-member court. In a recent case that invalidated Texas’ homosexual sodomy law, Scalia himself accused the six-justice majority of abandoning neutrality and “tak(ing) sides in the culture war.” That raises the obvious question: If their judgment can be so dubious on an issue of constitutional rights, why should his judgment — or any of the others’ — be sacrosanct on the question of individual impartiality?

It is almost surely too late to do anything about Scalia’s determination to participate in the Cheney case. He has stated his position forcefully, and it is unlikely that his colleagues will take the initiative to revisit the issue; after all, it was they who referred the disqualification motion to him in the first place, citing the court’s historical practice.

But it is not too late to address the broader policy problem. Judicial disqualification is a serious matter for the Supreme Court, which depends on public confidence for its legitimacy. In the future, Rehnquist could demonstrate real leadership by referring disqualification issues to the court itself, to be decided by a vote of all nine justices. If he continues to avoid the question, however, Congress should step in by enacting a statute mandating full consideration every time a justice’s impartiality is in dispute. The reputation of the Supreme Court is at stake. Surely that is too important to rest in the hands of any individual justice.

Erwin Chemerinsky is a professor of law and political science at the University of Southern California. Steven Lubet is a professor of law at Northwestern University.