First, an en banc rehearing may be needed to “secure or maintain uniformity of the court’s decisions.” A three-judge panel is not allowed to overrule old precedents, even when precedents are in conflict; only the full court can do so, en banc.

Second, en banc rehearing is appropriate for what the federal appellate rules call cases of “exceptional importance.” For the D.C. Circuit, this standard has been met almost exclusively by cases raising serious constitutional issues. Over the past decade seven of the nine cases reheard en banc raised difficult questions of constitutional law, such as the rights of Guantanamo detainees or of terminally ill patients.

Cases that will substantially affect the court’s own workings also can be deemed of “exceptional importance.” In 2011, the court sat en banc to decide whether taxpayers could file lawsuits challenging IRS procedures for obtaining tax refunds.

Halbig checks none of these boxes.