WASHINGTON — A federal judge on Thursday rejected the Justice Department’s request to resume a key part of its inquiry into former President Donald J. Trump’s handling of sensitive government records and appointed an outside arbiter to review thousands of documents seized last month from his Florida residence.
The judge, Aileen M. Cannon, declined to lift any part of an order she issued last week that barred the department from using the documents, including about 100 marked classified, in its investigation until the arbiter, known as a special master, had completed a review.
In her 10-page decision, Judge Cannon appointed a special master suggested by the Trump legal team and agreed upon by the government: Raymond J. Dearie, a semiretired judge from the Federal District Court for the Eastern District of New York.
Judge Dearie will now have the authority to sift through more than 11,000 records the F.B.I. carted away from Mr. Trump’s estate, Mar-a-Lago, on Aug. 8. The move was a blow to the Justice Department, almost certain to significantly delay its investigation into whether the former president unlawfully retained national defense records or obstructed repeated attempts by federal officials to retrieve them.
The department had asked Judge Cannon to lift restrictions on its use of documents with classification markings and set a Thursday deadline for her to respond before it said it would ask an appeals court to intervene. The department is now planning to appeal the decision, and top officials were meeting to discuss the timing of their filing, according to a senior law enforcement official.
Judge Cannon’s order was the latest turn in what has now become a protracted and politically fraught court battle over the trove of documents seized in the search of Mar-a-Lago.
While Judge Cannon’s order was a victory for Mr. Trump and his legal team, she also made two significant concessions to the government.
She said, for instance, that Judge Dearie should first look at the classified documents and “thereafter consider prompt adjustments to the court’s orders as necessary.” That raised the possibility that Judge Dearie might quickly clear the items and the F.B.I. would then regain unrestricted use of them in its criminal inquiry. In her order, Judge Cannon said the special master should try to finish his review by Nov. 30.
Judge Cannon also clarified her temporary ban on the Justice Department’s investigation. While the department could not present the seized documents to a grand jury or ask witnesses about their contents, she said, the F.B.I. could continue to investigate “the movement and storage of seized materials, including documents marked as classified, without discussion of their contents.”
More on the Trump Documents Inquiry
Still, Judge Cannon, whom Mr. Trump appointed in November 2020, declined to back down on having the special master vet those documents, too — and making the F.B.I. wait, at least for now, to have full access to them in its investigation.
In her order, Judge Cannon took pains to describe herself as mindful of the traditional reluctance of the judicial branch to intrude on executive authority in national security matters. But she wrote that her court could not “abdicate its control over questions of privilege and does not find the government’s argument sufficiently convincing as presented.”
Among other things, she went on, the government had not suggested there was any “identifiable emergency or imminent disclosure of classified information arising from” Mr. Trump’s retention of the materials. Instead, she added, “the unwarranted disclosures that float in the background have been leaks to the media after the underlying seizure.”
In naming Judge Dearie as special master, Judge Cannon did not address an issue the Justice Department had flagged in saying it was open to his appointment: As a semiretired judge on senior active status, he occasionally hears cases, and active judges are not supposed to have outside employment.
Judge Cannon said Mr. Trump would pay the entire cost of Judge Dearie’s compensation and expenses, along with the cost of support staff or advisers he needs, given that Mr. Trump had requested a special master.
Asked about the possibility of being indicted in the investigation, Mr. Trump told a conservative radio host on Thursday that there would be “problems in this country the likes of which perhaps we’ve never seen before.”
Last week, Judge Cannon issued an order announcing that she would appoint a special master to go over the materials to set aside any potentially covered by attorney-client privilege or, in a legally disputed move, executive privilege. She also prevented prosecutors from using any of the records in its investigation in the meantime.
But as part of her order, Judge Cannon permitted the government to continue using the documents for a national security risk assessment and a classification review.
Days later, the Justice Department asked Judge Cannon to stay parts of her order, requesting that the F.B.I. be allowed to resume investigating matters related to about 100 of the seized files marked as classified. The department argued that the bureau’s criminal investigation of the files was “inextricably linked” to the separate national-security reviews that she had said could continue.
At the same time, the Justice Department told Judge Cannon that if she did not agree to its requests for a stay by Thursday, it would ask the appeals court to intervene.
In effect, the government had sought a compromise, acquiescing to Judge Cannon’s decision to impose a special master and, at least temporarily, to bar F.B.I. agents and prosecutors from working further with the overwhelming majority of the seized documents and other records. In return, the Justice Department asked Judge Cannon to let its investigators continue working with a smaller batch.
To make their point, lawyers for the Justice Department singled out nearly 50 empty folders bearing classified banners that were found during the search of Mar-a-Lago. The lawyers said the F.B.I. needed to investigate what happened to the contents of the folders so intelligence officials could determine whether national security had been compromised.
The Office of the Director of National Intelligence has also said that after Judge Cannon’s order, it paused its risk assessment and classification review. In her ruling on Thursday, she expressed doubt about whether the government could no longer conduct such an assessment without the criminal investigation proceeding — even as she put forward a very narrow interpretation of her initial order.
Judge Cannon also responded to criticism that she had put too much weight on Mr. Trump’s status as a former president in deciding that a special master with a broad mandate was justified. Critics have said that she violated the principle that the law is supposed to be evenhanded and treat everyone equally and that she has shown him special deference.
She wrote that “the principles of equity require the court to consider the specific context at issue, and that consideration is inherently impacted by the position formerly held” by Mr. Trump.
She added that she steadfastly believed that appointing a special master to review the seized materials and temporarily barring the government from using them was principled and necessary “to ensure at least the appearance of fairness and integrity under unprecedented circumstances.”