As discussed in the NYT regarding the FBI warrant executed on Mar-a-Lago
In particular, a third law the warrant references was Section 793, which carries a penalty of up to 10 years in prison per offense. Better known as the Espionage Act, it was enacted by Congress during World War I, decades before President Harry S. Truman issued an executive order creating the modern classification system for the executive branch.
As a result, the Espionage Act makes no reference to whether a document has been deemed classified. Instead, it makes it a crime to retain, without authorization, documents related to the national defense that could be used to harm the United States or aid a foreign adversary.
Prosecutors could argue that a document meets that act’s standard regardless of whether Mr. Trump had pronounced it unclassified short before leaving office; by the same token, defense lawyers could argue that it fell short of that standard regardless of how it had been marked.
“Because the Espionage Act speaks in terms of national defense information, it leaves open the possibility that such information could be unclassified as long as an agency is still taking steps to protect it from disclosure,” said Steven Aftergood, who runs the Project on Government Secrecy at the Federation of American Scientists in Washington.
Are there examples of successful prosecution under the Espionage Act (and in particular Section 793) after the classification system was adopted, even for unclassified materials?