The federal judge overseeing former President Donald J. Trump’s prosecution on charges of illegally holding on to sensitive national security documents denied on Monday the government’s request to keep secret a list of witnesses with whom Mr. Trump has been barred from discussing his case.

The ruling by Judge Aileen M. Cannon, in the Southern District of Florida, means that some or all of the list of 84 witnesses could at some point become public, offering further details about the shape and scope of the case that the special counsel Jack Smith has brought against Mr. Trump.

The government’s request to keep the names of the witnesses secret “does not offer a particularized basis to justify sealing the list from public view,” Judge Cannon wrote in her brief order. “It does not explain why partial sealing, redaction or means other than sealing are unavailable or unsatisfactory, and it does not specify the duration of any proposed seal.”

One of the conditions that a federal magistrate judge placed on Mr. Trump when he walked free from his arraignment this month was a provision prohibiting him from discussing the facts in his indictment with any witnesses in the case. The indictment accused Mr. Trump of willfully retaining 31 individual national security documents and obstructing the government’s repeated efforts to reclaim them.

While the identities of the witnesses remain unknown, many of them are believed to be aides and advisers close to Mr. Trump — among them, several who work or worked with him at Mar-a-Lago, his private club and residence in Florida. As part of the conditions the magistrate judge imposed, Mr. Trump was also barred from discussing the case with his co-defendant, Walt Nauta, who remains his personal aide.

Last week, as Mr. Smith’s prosecutors gave the witness list to Mr. Trump’s legal team, they asked Judge Cannon if they could keep the names under seal. In their request, the prosecutors noted that Mr. Trump’s lawyers had not taken a position on the request to seal the list.

Then on Monday, a group of news media companies including The New York Times filed their own motion asking Judge Cannon to make the list public, saying that the case against Mr. Trump was “one of the most consequential criminal cases in the nation’s history.”

“The American public’s interest in this matter, and need to monitor its progress every step of the way, cannot be overstated,” the news organizations wrote.

In her ruling, Judge Cannon said the petition by the news media was moot, given that she had denied the government’s request to seal. It remained unclear from the judge’s order if Mr. Smith’s office would ultimately post the witness list — perhaps redacted in some way — on a public docket or if prosecutors would simply be unable to stop Mr. Trump’s lawyers from making the list of names public should they choose to do so.

Peter Carr, a spokesman for Mr. Smith, did not respond to messages seeking comment.

In a separate order issued on Monday, Judge Cannon asked Mr. Trump’s legal team to respond by July 6 to Mr. Smith’s request to delay the start of the trial until Dec. 11.

Judge Cannon also scheduled a hearing for July 14 for the parties to discuss how to handle the significant amount of highly sensitive material involved in the case under a law known as the Classified Information Procedures Act. That hearing will be conducted mostly, if not entirely, under seal.