Businessman Yevgeniy Prigozhin, left, serves food to then-Russian Prime Minister Vladimir Putin, center, during dinner at Prigozhin's restaurant outside Moscow on Nov. 11, 2011. (Misha Japaridze/AP)

A federal judge has approved a request to tightly control how evidence is shared with a Russian company accused of funding an Internet trolling operation to mislead American voters in the 2016 election.

The dispute over how to protect sensitive materials from disclosure had threatened to stall prosecution of the sole defendant to appear in court to face charges in the indictment of Russian entities under special counsel Robert S. Mueller III.

U.S. District Judge Dabney L. Friedrich of the District of Columbia said Friday that federal prosecutors gave “ample good cause” that identifying sources in the probe could tip off Russian intelligence and other foreign services to ongoing national security investigations and undermine efforts to protect future elections from similar interference.

Friedrich barred the U.S.-based attorneys for Concord Management and Consulting, which was indicted in February along with 13 Russian individuals and two other companies from sharing sensitive case materials from any foreign national without court approval.

Concord denies the allegations, and its attorneys said it was critical that their defense strategy include co-defendant Yevgeniy Viktorovich Prigozhin, a catering magnate known as “Putin’s chef” because of his ties to Russian President Vladi­mir Putin.

Prigozhin and Concord were hit with U.S. sanctions over Russia’s occupation of Crimea and military actions in Ukraine in 2016, and they were hit again this March based on “malicious cyber-enabled activities.”

In a seven-page opinion, Friedrich ruled, “Concord’s right to prepare and present a full defense at trial does not depend on Prigozhin having access to sensitive discovery materials, at least not at this early stage of the prosecution.”

The judge said the issue could be revisited after a trial date is set.

Prigozhin, Concord and a catering company were each charged with criminally interfering with the election through a disinformation campaign to persuade voters to support then-Republican presidential nominee Donald Trump and back away from Democratic nominee Hillary Clinton. The Internet Research Agency, based in St. Petersburg, was accused of being the hub of the operation in the indictment.

Prosecutors warned that Concord’s requests would reveal government investigative techniques and identify cooperating individuals and companies as well as personal information of U.S. identity theft victims whose data was used in the plot.

They said Prigozhin was using a company with minimal business in the United States as a stalking horse to compromise the investigation while evading criminal prosecution himself, and they proposed he appear in court as a condition to access materials.

Friedrich barred any individual or entity, including Prigozhin or any other foreign national other than Concord’s defense team with the Reed Smith law firm, from accessing sensitive materials without her approval. Sensitive data, the order said, must be stored in a U.S. office of the firm, reviewed only when a designated firm employee is present and “not disclosed, transported or transmitted outside of the United States.”

Friedrich said Concord’s attorneys may later ask to disclose sensitive evidence at its offices to others, including potential witnesses, their counsel and defense team vendors, by submitting their names outside of the presence of prosecutors to an independent, court-appointed “firewall attorney” nominated by the U.S. government, who could alert the judge to any government concerns.

Prosecutors have told Concord’s lawyers that they plan to turn over voluminous records, much of it related to hundreds of fake social media accounts but also some that includes “uncharged co-conspirators.”