Grand jury secrecy is important. It allows investigations to be conducted discreetly, and it protects reputations. The Federal Rules of Criminal Procedure allow disclosure of grand jury materials in only a few circumstances, none of which include completing the historical record.

The Justice Department, under presidents of both parties, has said those rules are the end of the matter. Though judges are not listed among the people covered by grand jury secrecy rules, department officials said, they may not disregard them.

But that argument has until recently gotten very little traction. In 2012, a committee of federal judges rejected an Obama administration proposal to add a limited exception to the rules allowing the disclosure of some historical records. Such an exception, the committee said, was a solution in search of a problem.

“In the rare cases where disclosure of historic materials had been sought,” a committee report said, “the district judges acted reasonably in referring to their inherent authority. Therefore, there is no need for a rule on the subject.”

The D.C. Circuit case that unsettled that consensus in April concerned an abduction reminiscent of the murder in October of the Saudi journalist Jamal Khashoggi. In 1956, Jesús de Galíndez Suárez, a professor at Columbia University, disappeared from the streets of New York City.

Professor Galíndez seems to have been kidnapped, flown to the Dominican Republic and murdered by associates of its dictator, Rafael Trujillo. A grand jury investigated whether John Joseph Frank, a former F.B.I. agent, had played a role in the matter. Stuart A. McKeever, a historian, sought access to those records.

Judge Douglas H. Ginsburg, writing for the majority, rejected Mr. McKeever’s request, saying courts were powerless to grant it. That was bad news for historians, but it did not directly address the status of the Mueller report.