The federal appeals court in Washington on Friday ruled that grand-jury testimony and information may be disclosed only to prosecutors, defendants and other grand juries and that judges may not carve out exceptions to the secrecy already mandated by the Federal Rules of Criminal Procedure.

The split decision, by a three-judge panel of the U.S. Court of Appeals for the D.C. Circuit, could lead to further confusion over the public release of the report written by special counsel Robert S. Mueller III documenting his investigation of Russian interference in the 2016 presidential election, as well as related investigative materials.

“Every page of the ‘confidential report’ ” by Mueller, Justice Department spokeswoman Kerri Kupec said in a statement Thursday, “was marked ‘May Contain Material Protected Under Fed. R Crim. P. 6(e)’ — a law that protects confidential grand jury information — and therefore could not be publicly released.”

But the court’s ruling also affirmed that grand-jury materials could be shared with the House of Representatives under an exception for “judicial proceedings,” citing a 1974 ruling by U.S. District Judge John J. Sirica during the investigation of President Richard M. Nixon that the House “in this setting acts simply as another grand jury.”

Within two hours of Friday’s ruling, the government had already noted the appeals court’s opinion in a court filing opposing a petition by three prominent legal analysts seeking to further unseal grand-jury materials gathered by special prosecutor Leon Jaworski in the legal case against Nixon. A district judge in Washington in October ordered Jaworski’s “road map” report to Congress unsealed. The analysts sought further investigative materials, saying they could offer a possible precedent and guide for Mueller, and the government appealed.

The ruling was written by Judge Douglas H. Ginsburg, joined by Judge Gregory G. Katsas, with Judge Sri Srinivasan dissenting.

The plaintiff, author Stuart A. McKeever, said he planned to appeal.

Justice Department spokeswoman Kelly Laco said in a statement that the department was “pleased that the court re-affirmed the Department of Justice’s long-standing position and Supreme Court precedent that the proper functioning of the grand jury depends on the confidentiality of proceedings. The Department of Justice will continue to defend the long established tradition of protecting grand jury information.

The decision adds to a body of conflicting appeals-court decisions about whether federal judges have expansive powers or operate under tight restrictions about when grand-jury materials can be shared.

In the past, the D.C. Circuit has permitted disclosure of grand-jury materials when no specific exception applied, including in 2011, when a court released transcripts of Nixon’s post-resignation questioning by special prosecutors in 1975 before grand jurors, and in 2007 in connection with the grand-jury subpoena of New York Times journalist Judith Miller.

“This issue keeps coming back, whether the grand jury must be sacrosanct forever,” said former federal prosecutor Laurie Levenson, now a professor at Loyola Law School in Los Angeles. “I ran grand juries, and secrecy should be the starting point. But that’s the tension, between the benefits of secrecy versus opening the cases of historical interest. I wouldn’t be surprised if Congress or the Supreme Court, or both, take a hard look at this.”

Federal Rules of Criminal Procedure Rule 6(e) discusses who must maintain absolute secrecy when discussing grand-jury matters — grand jurors, court reporters, prosecutors — and the exceptions to that secrecy. Ginsburg wrote that the rule is absolute and that district judges have no authority to create exceptions for authors, journalists, analysts or anyone else.

“Our understanding that deviations from the detailed list of exceptions in Rule 6(e) are not permitted is fully in keeping with Supreme Court precedent,” Ginsburg wrote.

In the case at the D.C. Circuit, McKeever is seeking records from a 1957 grand jury that investigated the abduction and killing of Columbia University professor Jesús de Galíndez Suárez. Galíndez was believed to have been abducted from the streets of New York City and flown to the Dominican Republic, where he and the pilot were reportedly killed.

John Joseph Frank, a former FBI agent and CIA lawyer who worked for Dominican Republic dictator Rafael Trujillo, was indicted on a charge of failure to register as a foreign agent but was never charged in the deaths of Galíndez or the pilot, Gerald L. Murphy.

U.S. District Judge Royce C. Lamberth ruled in May 2017 that he had “inherent supervisory authority” to disclose grand-jury matters, then denied McKeever’s request anyway as overbroad.

McKeever appealed, and the case was being watched closely for its possible impact on the Mueller investigation. In the meantime, Attorney General William P. Barr has withheld releasing Mueller’s report, to Congress or the public, until he can redact items from the report that are related to the grand jury.

“The attorney general could, were he so inclined, seek permission from the court under existing statutes to release unredacted portions of the grand-jury transcripts,” said Jeffrey Fagan, a Columbia Law School professor. “The issue isn’t carving out new exceptions or writing new rules but being crafty in how he makes the request to the court under the current rules. The existing rules should be enough for a judge to rule on release.”

The exceptions to Rule 6(e)’s secrecy requirements allow grand-jury disclosures to federal prosecutors or any government personnel — including state or foreign governments — whom prosecutors deem “necessary to assist in performing that attorney’s duty to enforce federal criminal law.”

The exceptions state that prosecutors “may disclose any grand-jury matter to another federal grand jury” and may disclose grand-jury information involving foreign intelligence to “any federal law enforcement . . . or national security official,” as well as to help prevent a foreign attack.

Also, the exceptions authorize grand-jury disclosure “in connection with a judicial proceeding,” “at the request of a defendant” if the information may exonerate that person and at the government’s request for use in foreign, state, trial or military prosecutions.

Srinivasan’s dissent said that when the circuit court upheld Sirica’s 1974 ruling, it “affirmed his understanding that a district court retains discretion to release grand jury materials outside the Rule 6(e) exception.”

Ginsburg, in the majority ruling, wrote the circuit court was interpreting Sirica’s 1974 ruling “as fitting within the Rule 6 exception for ‘judicial proceedings.’ ”

McKeever had argued that the passage of time made it possible that all interested parties in the Frank case were dead. But Ginsburg wrote that “privacy interests can persist even after a person’s death,” that a potential future release of information might chill a witness’s willingness to testify and that creating more exceptions to Rule 6(e) might further discourage witness cooperation.

Citing a 1992 ruling, Ginsburg added that “the grand jury is an institution separate from the courts, over whose functioning the courts do not preside.”

McKeever said Friday he had not read the ruling and planned to consult with lawyers who assisted him. But he added, “My intent is to take this further.”