The Justice Department argued in a newly unsealed court filing that former President Donald Trump mischaracterized White House documents he retained after leaving office as “personal,” accusing Trump of engaging in a “shell game” to shield documents from criminal investigators.

Prosecutors claimed in the filing, which was unsealed Monday by U.S. District Court Judge Aileen Cannon, that Trump tried to limit investigators’ access to materials seized by the FBI in August from his Mar-a-Lago estate by incorrectly claiming they were his personal property. Presidents may declare certain records “personal” under federal law if they have no decision-making value to future administrations.

However, the DOJ believes Trump’s claim is self-defeating. Prosecutors argue that if the records are truly personal, there is no reason to keep them from investigators.

The Department of Justice’s argument came in response to a request from U.S. District Court Judge Raymond Dearie, whom Cannon appointed as a “special master” to review the documents seized from Trump’s estate for potentially privileged records. Dearie requested that the DOJ and Trump’s attorneys brief him on executive privilege and the classification of White House records as “personal,” two sensitive issues that are rarely raised in criminal investigations.

The special master’s appointment by Cannon slowed the DOJ’s pursuit of a potential criminal case against Trump for keeping highly sensitive national security documents at Mar-a-Lago after he left office. Dearie is expected to make a decision next month on whether to recommend that prosecutors be granted access to the documents, though Cannon has the final say. Prosecutors say their evidence suggests Trump or his associates also attempted to obstruct DOJ’s efforts to retrieve the records.

In his own brief, Trump argued that by simply moving thousands of documents from the White House to Mar-a-Lago, he implicitly labeled them “personal,” and his lawyers argue that the DOJ has no legal recourse to challenge that designation. Trump also claimed that executive privilege may apply to some of the records, despite the DOJ’s claim that shielding sensitive government records from the Executive Branch that created them would be unprecedented.

Prosecutors argued that accepting Trump’s argument that the documents essentially became personal solely because he kept them would create a gaping hole in the Presidential Records Act, which Congress passed in 1978 declaring presidential records to be government property.

Bratt wrote that Trump “appears to be claiming that he can unilaterally ‘deem’ otherwise Presidential records to be personal records by fiat.” “Such a reading of the PRA would render the statute’s entire purpose null and void by allowing a President to designate all of his official records as ‘personal’ records and then remove them upon leaving the White House.” It would reduce the PRA’s detailed definitions of “Presidential records” and “personal records” to mere guidelines.”

Prosecutors were also irritated by Trump’s attempt to claim executive privilege over some of the “personal” records. Any documents that are purely personal in nature, according to Bratt, cannot be protected by executive privilege, a principle intended to protect sensitive government records and internal White House communications.

Jackson’s decision, made a decade ago by a district court judge appointed by President Barack Obama, is not binding on any other judges. However, it has taken on exaggerated proportions in the Mar-a-Lago document battle, in part because there are only a few court cases interpreting the presidential records law, which was enacted in the midst of protracted legal wrangling over former President Richard Nixon’s files.

The Department of Justice claims that Jackson’s 2012 opinion is inapplicable to the current dispute, in which the National Archives has challenged Trump’s designation of the records as “personal.” The Presidential Records Act allows the Archives to take steps to recover documents it considers to be government property.

Trump claims that the only legal option for the Archives and the Justice Department would have been to sue him for the records’ return, rather than launch a grand jury investigation and potential criminal prosecution. Trump has also spent recent months making unsubstantiated claims that the leadership of the National Archives is politically biased against him.

Dearie is expected to make a decision next month on which, if any, of the approximately 3,000 seized documents should be withheld from investigators. Prosecutors and Trump will then be able to discuss their differences with Cannon. Furthermore, the Justice Department has an appeal pending at the 11th Circuit Court of Appeals, requesting that the entire process Cannon ordered at Trump’s request be halted.