David Laufman said there would be evidence if Trump declassified the Mar-a-Lago documents.
Laufman, a former DOJ official, investigated Hillary Clinton's handling of classified records.
Trump said he had a "standing order" to declassify, but ex-officials have pushed back on the claim.
A former Department of Justice official has pushed back on Trump's claim that he had broadly declassified all the documents held at Mar-a-Lago, saying if that were the case there would be evidence to back it up.
Trump made the claim after the FBI raided his Mar-a-Lago residence in Florida last week. The search was part of a Justice Department investigation into potential violations of three laws related to the handling of government records. Court documents showed 11 sets of classified materials were seized during the search.
Trump has denied any wrongdoing and claimed he had a standing order to declassify documents that were removed from the Oval Office and taken to his residence. Presidential records, classified or not, are public property and by law are managed by the National Archives when a president leaves office.
David Laufman, the former chief of the Justice Department's counterintelligence division, dismissed the idea of the standing order or broad declassification.
"It can't just be an idea in his head," Laufman, who led the investigation into Hillary Clinton's emails and handling of classified documents, told CNN. "Programs and officials would have been notified. There is no evidence they were."
Presidents have broad authority to declassify documents, but former Trump administration officials told CNN there is a process that is followed. The process typically involves documenting the declassification and notifying agencies, such as the CIA, NSA, or Defense Department, among others.
Laufman had previously said the documents Trump was holding at Mar-a-Lago were particularly "stunning" and "egregious" due to their level of classification. According to court records, one set of documents was labeled "Sensitive Compartmented Information," the highest level of sensitivity a classified document can be designated.
Former Trump White House officials also pushed back on Trump's claim that he had a "standing order" to declassify documents when they were transported. Two of Trump's former chiefs of staff, John Kelly and Mick Mulvaney, told CNN they'd never heard of such an order.
"Nothing approaching an order that foolish was ever given," Kelly, who was chief of staff for nearly a year and a half from 2017 to 2019, said. "And I can't imagine anyone that worked at the White House after me that would have simply shrugged their shoulders and allowed that order to go forward without dying in the ditch trying to stop it."
CNN spoke with a total of 18 former Trump administration officials, some unnamed, who all said they had never heard of such an order, with several laughing at the idea and suggesting Trump had made it up.