You need to fire whomever does your research.
"Some secrets, such as information related to nuclear weapons, are handled separately under a specific statutory scheme that Congress has adopted under the Atomic Energy Act. Those secrets cannot be automatically declassified by the president alone and require, by law, extensive consultation with executive branch agencies.
In all cases, however, a formal procedure is required so governmental agencies know with certainty what has been declassified and decisions memorialized. A federal appeals court in a 2020 Freedom of Information Act case, New York Times v. CIA, underscored that point: “Declassification cannot occur unless designated officials follow specified procedures,” the court said.
As the new ABA Legal Fact Check notes, the extent of a president’s legal authority to unilaterally declassify materials — without following formal procedures — has yet to be challenged in court.
https://www.americanbar.org/news/abanews/aba-news-archives/2022/10/fact-check-presidential-authority/
In addition:
"Former President Donald Trump acknowledged on tape in a 2021 meeting that he had retained “secret” military information that he had not declassified, according to a transcript of the audio recording obtained by CNN.
“As president, I could have declassified, but now I can’t,” Trump says, according to the transcript."
https://www.cnn.com/2023/06/09/politics/trump-tape-didnt-declassify-secret-information/index.html
"In 2010, the conservative group Judicial Watch sued the National Archives and Records Administration, arguing audio tapes kept by Clinton for interviews he did with historian Taylor Branch during his years in office -- and which he afterward allegedly kept in a sock drawer -- were "presidential records" and should be made available to the public.
U.S. District Court Judge Amy Berman Jackson dismissed the case, and Trump and his allies have taken to quoting different parts of her opinion in their defense.
The Presidential Records Act does contain an exception for personal records, according to Baron, including items such as "diaries, journals, and other personal notes that were never used in the transaction of government business."
"President Trump had the right to keep those types of records. But the argument being made by some that he had some kind of absolute authority while president to declare classified records or other official records about government business as his personal records is absurd in its face," he said. "It is also contrary to law. The decision by Judge Jackson cited prior precedent from the D.C. Circuit that stands for the opposite proposition."
That citation included in Jackson's opinion reads, in part, that the Presidential Records Act "does not bestow on the president the power to assert sweeping authority over whatever materials he chooses to designate as presidential records without any possibility of judicial review."
"Judge Jackson went on to speculate about the level of deference to be afforded a president making a categorical decision about whether records of his were personal, but she never ruled on that issue," Baron said. "Instead, the case was dismissed on the grounds that plaintiff had no standing to compel the Archivist to seize materials not in the government’s possession."
https://news.yahoo.com/trump-makes-legal-claims-classified-225100248.html?
In any event, whether documents are of a personal nature is to be decided while the president is still in office.